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Monday, 31 March 2014

Landscape heterogeneity and population range: species specific importance. PLoS ONE March 2014

Landscape Heterogeneity–Biodiversity Relationship: Effect of Range Size
Authors and Affiliations
Naoki Katayama

Biodiversity Division, National Institute for Agro-Environmental Sciences, Tsukuba-shi, Ibaraki, Japan
Tatsuya Amano
Conservation Science Group, Department of Zoology, University of Cambridge, Cambridge, United Kingdom
Shoji Naoe, Isamu Komatsu, Tadashi Miyashita
Laboratory of Biodiversity Science, School of Agricultural and Life Sciences, University of Tokyo, Tokyo, Japan
Takehisa Yamakita
Japan Agency for Marine-Earth Science and Technology (JAMSTEC), Yokosuka, Kanagawa, Japan
Shin-ichi Takagawa
The Nature Conservation Society of Japan, Chuo-ku, Tokyo, Japan
Naoto Sato
Biodiversity Center of Japan, Kamiyoshida, Fujiyoshida-shi, Yamanashi, Japan
Mutsuyuki Ueta
Japan Bird Research Association, Fuchu-shi, Tokyo, Japan

Published: March 27, 2014
DOI: 10.1371/journal.pone.0093359

The importance of landscape heterogeneity to biodiversity may depend on the size of the geographic range of species, which in turn can reflect species traits (such as habitat generalization) and the effects of historical and contemporary land covers. We used nationwide bird survey data from Japan, where heterogeneous landscapes predominate, to test the hypothesis that wide-ranging species are positively associated with landscape heterogeneity in terms of species richness and abundance, whereas narrow-ranging species are positively associated with landscape homogeneity in the form of either open or forest habitats. We used simultaneous autoregressive models to explore the effects of climate, evapotranspiration, and landscape heterogeneity on the richness and abundance of breeding land-bird species. The richness of wide-ranging species and the total species richness were highest in heterogeneous landscapes, where many wide-ranging species showed the highest abundance. In contrast, the richness of narrow-ranging species was not highest in heterogeneous landscapes; most of those species were abundant in either open or forest landscapes. Moreover, in open landscapes, narrow-ranging species increased their species richness with decreasing temperature. These results indicate that heterogeneous landscapes are associated with rich bird diversity but that most narrow-ranging species prefer homogeneous landscapes—particularly open habitats in colder regions, where grasslands have historically predominated. There is a need to reassess the generality of the heterogeneity-biodiversity relationship, with attention to the characteristics of species assemblages determined by environments at large spatiotemporal scales.

Example Figure
Figure 5. Relationship between number of habitat types used by a species and range size.
For range size, the number of 20-km-square grids occupied by the species is used for 107 ou
t of 113 terrestrial bird species in Japan (except for six raptor species without range-size data). Values inside bars and error bars indicate sample size and standard error, respectively.

The authors conclude that there are a number of variables at work in defining the solution to ensuring biodiversity in bird populations. For each type of population, specialist to generalist, there would need to be an inspection of the range of habitat used. This would not only be the geographical location but also the local climate too, and possibly other factors of the macro-environment.

Wednesday, 26 March 2014

Winning the battle with help from a Cuckoo in the nest - unexpected benefits if you can stand the smell. Science journal paper - March 2014

From Parasitism to Mutualism: Unexpected Interactions Between a Cuckoo and Its Host

Science 21 March 2014: Vol. 343 no. 6177 pp. 1350-1352 
DOI: 10.1126/science.1249008

Daniela Canestrari 1,2
Diana Bolopo 3
Ted C. J. Turlings 4
Gregory Röder 4
José M. Marcos 3
Vittorio Baglione 3,5

1: Department of Biology of Organisms and Systems, University of Oviedo, Oviedo, Spain. 
2: Research Unit of Biodiversity, Unidad Mixta de Investigación para la Biodivesidad, Consejo Superior de Investigaciones Científicas, University of Oviedo, Principado de Asturias, Oviedo, Spain. 
3: Department of Agro-forestry, University of Valladolid, Vallodolid, Spain. 
4: Institute of Biology, University of Neuchâtel, Neuchâtel, Switzerland. 
5: Sustainable Forest Management Research Institute, Palencia, Spain.

Avian brood parasites lay eggs in the nests of other birds, which raise the unrelated chicks and typically suffer partial or complete loss of their own brood. However, carrion crows (Corvus corone corone) can benefit from parasitism by the great spotted cuckoo (Clamator glandarius). Parasitized nests have lower rates of predation-induced failure due to production of a repellent secretion by cuckoo chicks, but among nests that are successful, those with cuckoo chicks fledge fewer crows. The outcome of these counterbalancing effects fluctuates between parasitism and mutualism each season, depending on the intensity of predation pressure.

The authors investigated (i) whether the great spotted cuckoo provides a benefit to crows and whether such benefit could derive from the ability of cuckoo chicks to deter predators with a noxious secretion that they release when harassed, and (ii) whether the outcome of host-parasite interaction varies across seasons, depending on the intensity of predator pressure. 

The authors used data collected over 16 years to analyze the effect of the parasite on crow reproductive success. In the studied population, crows breed cooperatively and raise a single annual brood, although they can renest in case of early nest failure. Each season, nests were monitored to record laying date, clutch size, presence of parasitic eggs, hatching success, and number of fledglings produced (n = 741 nests in 109 territories). To test whether crow clutches benefit from being parasitized, they transferred cuckoo hatchlings (one or two per nest) into synchronous nonparasitized nestswhereas unmanipulated parasitized and non-parasitized nests served as controls. Furthermore, to control for the effect of the manipulation (adding or removing chicks), in a subsequent
experiment they moved one crow chick between synchronous nonparasitized nests and kept unmanipulated nests for control. Finally, they used gas chromatography and mass spectrometry to analyze the chemical composition of cuckoo cloacal secretions, and performed repellence tests on species belonging to the three main groups of crow nest predators (mammals, corvids, and raptors). Seventeen quasi-feral cats were each presented with 10 pieces of chicken meat, treated either with water or natural cuckoo secretion. Seven captive crows and seven captive raptors were each offered six pieces of meat (three treated and three control), one at a time.

Fig. 1. Probability of success of experimental and control nests: shows an success with cuckoo added.
[n, number of nests].

Overall, throughout the 16 seasons, parasitized and nonparasitized broods did not significantly differ in the number of crows fledged, though results suggest a slight benefit from raising a cuckoo. 
The results of the translocation experiment show a causal link between the presence of a parasitic chick and greater nest success. 
Among parasitized nests, those from which cuckoos were removed failed significantly more often than control nests, whereas among non-parasitized nests, the addition of cuckoo chicks resulted in significantly increased success (Fig. 1). 
In sharp contrast to the effect of cuckoo chick transfer, nests in which a crow chick was added showed no difference in success rate from those that were not manipulated or those from which a crow chick was removed, though the difference was suggestive of a reduction.

The most plausible mechanism driving the reduction of failure in nests with cuckoos is predator repellence by a malodorous cloacal secretion that parasitic chicks void when grabbed. This secretion is only produced by cuckoo nestlings (0 of 23 captured adults showed it) and can be copious (up to 1.2ml released by a 45g chick). The chemical analysis of cuckoo secretion revealed a mix of caustic and repulsive compounds, dominated by acids, indoles, phenols, and several sulfur containing compounds that are known to repel mammals and birds. Further chemical analyses confirmed the distinct volatile profile of a cuckoo’s secretion as compared with feces of both cuckoos and crows, and its defensive function was confirmed by repellence tests. Eight of nine cats ate all 10 pieces of control meat, whereas only one of eight cats took a bite from treated meat. When we reversed the treatment for 9 of the original 17 cats, those offered control meat (n = 5) ate all the pieces, but none bit the treated meat (n = 4). Crows also showed avoidance of the treated meat as did the raptors.

The authors demonstrate that the consequences of brood parasitism can be beneficial and that this benefit may be context-dependent, possibly preventing the evolution of host defenses, particularly when a nonevicting cuckoo parasitizes a larger host.

Friday, 21 March 2014

Acoustic monitoring of seabird colonies to estimate relative abundance of birds. Conservation Biology; March 2014

Vocal Activity as a Low Cost and Scalable Index of Seabird Colony Size.

Abraham L. Borker 1
Matthew W. McKown 1 
Joshua T. Ackerman 2
Collin A. Eagles-Smith 2 
Bernie R. Tershy 1 
Donald A. Croll 1

1-Department of Ecology and Evolutionary Biology, Center for Ocean Health, University of California Santa Cruz, Santa Cruz, CA 95060, U.S.A.

2-U.S. Geological Survey, Western Ecological Research Center, Davis Field Station, One Shields Avenue, University of California, Davis, CA 95616, U.S.A.

Conservation Biology 2014 Mar 14. doi: 10.1111/cobi.12264.

Although wildlife conservation actions have increased globally in number and complexity, the lack of scalable, cost-effective monitoring methods limits adaptive management and the evaluation of conservation efficacy. Automated sensors and computer-aided analyses provide a scalable and increasingly cost-effective tool for conservation monitoring. A key assumption of automated acoustic monitoring of birds is that measures of acoustic activity at colony sites are correlated with the relative abundance of nesting birds. We tested this assumption for nesting Forster's terns (Sterna forsteri) in San Francisco Bay for 2 breeding seasons. Sensors recorded ambient sound at 7 colonies that had 15-111 nests in 2009 and 2010. Colonies were spaced at least 250 m apart and ranged from 36 to 2,571 m2 . We used spectrogram cross-correlation to automate the detection of tern calls from recordings. We calculated mean seasonal call rate and compared it with mean active nest count at each colony. Acoustic activity explained 71% of the variation in nest abundance between breeding sites and 88% of the change in colony size between years. These results validate a primary assumption of acoustic indices; that is, for terns, acoustic activity is correlated to relative abundance, a fundamental step toward designing rigorous and scalable acoustic monitoring programs to measure the effectiveness of conservation actions for colonial birds and other acoustically active wildlife. La Actividad Vocal como un Índice Escalable y de Bajo Costo del Tamaño de Colonia de las Aves Marinas.

Example Figure
Figure 1. 
Seasonal mean acoustic call activity (calls per minute) relative to (a) mean nest abundance and (b) total nest abundance during the 2009 and 2010 breeding seasons of Forster's terns at colonies in San Francisco Bay, California. Black line is best fit from a linear mixed model incorporating nest abundance with site, year, and sensor type as random factors.

Thursday, 20 March 2014

Inverleith Park, Edinburgh: Boating Lake and Wildlife Pond on a rainy Spring Equinox morning in 2014

  After a couple of warm and calm Spring mornings, and being early for work, I thought I'd bring along my camera and visit Inverleith Park - today though there were gale force winds and rain. The birds were keeping warm and out of the wind, and wondering like the rest of us whether this really was the Spring Equinox.
On the lake today were: Mute Swan, Mallard, Tufted Duck, Feral Pigeon, Goosander, Coot, and Moorhen.

Bird Conservation International, Volume 24; Issue 01; March 2014 - Table of Contents with links to papers

VOLUME 24 - ISSUE 01 - March 2014

Table of Contents

The importance of northern Spanish farmland for wintering migratory passerines: a quantitative assessment
Bird Conservation International, Volume 24, Issue 01, March 2014, pp 1-16
doi: 10.1017/S0959270913000191, 
Published online by Cambridge University Press 03 Jun 2013

Hayfields enhance colony size of the Barn Swallow Hirundo rustica in northern Italy
Bird Conservation International, Volume 24, Issue 01, March 2014, pp 17-31
doi: 10.1017/S095927091300021X, 
Published online by Cambridge University Press 03 Jun 2013

Human disturbance and conspecifics influence display site selection by Great Bustards Otis tarda
Bird Conservation International, Volume 24, Issue 01, March 2014, pp 32-44
doi: 10.1017/S0959270913000142, 
Published online by Cambridge University Press 28 Mar 2013

Effect of mowing on productivity in the endangered Aquatic Warbler Acrocephalus paludicola
Bird Conservation International, Volume 24, Issue 01, March 2014, pp 45-58
doi: 10.1017/S0959270913000154, 
Published online by Cambridge University Press 28 Mar 2013

Molecular phylogeny of the South American sheldgeese with implications for conservation of Falkland Islands (Malvinas) and continental populations of the Ruddy-headed Goose Chloephaga rubidiceps and Upland Goose C. picta
Bird Conservation International, Volume 24, Issue 01, March 2014, pp 59-71
doi: 10.1017/S0959270913000178, 
Published online by Cambridge University Press 08 Apr 2013

Foraging ecology and choice of feeding habitat in the New Zealand Fairy Tern Sternula nereis davisae
Bird Conservation International, Volume 24, Issue 01, March 2014, pp 72-87
doi: 10.1017/S0959270913000312, 
Published online by Cambridge University Press 22 Jul 2013

Population status of the Madagascar Fish Eagle Haliaeetus vociferoides in 2005–2006
Bird Conservation International, Volume 24, Issue 01, March 2014, pp 88-99
doi: 10.1017/S0959270913000038, 
Published online by Cambridge University Press 28 Mar 2013

Distribution modelling of Eleonora’s Falcon Falco eleonorae Géné, 1839 occurrence in its wintering grounds: a niche-based approach with satellite telemetry data
Bird Conservation International, Volume 24, Issue 01, March 2014, pp 100-113
doi: 10.1017/S0959270913000361, 
Published online by Cambridge University Press 12 Aug 2013

Distribution and habitat use of the Austral Rail Rallus antarcticus and perspectives on its conservation
Bird Conservation International, Volume 24, Issue 01, March 2014, pp 114-125
doi: 10.1017/S0959270913000257, 
Published online by Cambridge University Press 17 Jun 2013

Wednesday, 19 March 2014

Increase in Adelie penguin breeding population in Ross Sea over last 10 years: PLoS ONE; March 2014

Trends in the Breeding Population of Adélie Penguins in the Ross Sea, 1981–2012: A Coincidence of Climate and Resource Extraction Effects

PLoS ONE 9(3): e91188. doi:10.1371/journal.pone.0091188

Phil O’B. Lyver, Mandy Barron, Stephen McNeill
Landcare Research, Lincoln, New Zealand
Kerry J. Barton
Bartonk Solutions, Nelson, New Zealand
David G. Ainley, Annie Pollard
H. T. Harvey & Associates Ecological Consultants, Los Gatos, California, United States of America
Shulamit Gordon
Antarctica New Zealand, Christchurch, New Zealand
Grant Ballard
Point Blue Conservation Science, Petaluma, California, United States of America
Peter R. Wilson

Auckland, New Zealand

Measurements of the size of Adélie penguin (Pygoscelis adeliae) colonies of the southern Ross Sea are among the longest biologic time series in the Antarctic. We present an assessment of recent annual variation and trends in abundance and growth rates of these colonies, adding to the published record not updated for more than two decades. High angle oblique aerial photographic surveys of colonies were acquired and penguins counted for the breeding seasons 1981–2012. In the last four years the numbers of Adélie penguins in the Ross and Beaufort Island colonies (southern Ross Sea metapopulation) reached their highest levels since aerial counts began in 1981. Results indicated that 855,625 pairs of Adélie penguins established breeding territories in the western Ross Sea, with just over a quarter (28%) of those in the southern portion, constituting a semi-isolated metapopulation (three colonies on Ross Island, one on nearby Beaufort Island). The southern population had a negative per capita growth rate of −0.019 during 1981–2000, followed by a positive per capita growth rate of 0.067 for 2001–2012. Colony growth rates for this metapopulation showed striking synchrony through time, indicating that large-scale factors influenced their annual growth. In contrast to the increased colony sizes in the southern population, the patterns of change among colonies of the northern Ross Sea were difficult to characterize. Trends were similar to southern colonies until the mid-1990s, after which the signal was lost owing to significantly reduced frequency of surveys. Both climate factors and recovery of whale populations likely played roles in the trends among southern colonies until 2000, after which depletion of another trophic competitor, the Antarctic toothfish (Dissostichus mawsoni), may explain the sharp increasing trend evident since then.

Figure 2. 
Time-series plots of the logged Adélie penguin colony counts at Cape Royds, Cape Bird, Cape Crozier and Beaufort Island, Antarctica from 1981 to 2012.

The linear regression trend lines are for the period 1981–2000.

Computational analysis of Canary Song to define the order and structure of the birdsong: Free Access PLoS Computational Biology paper

Long-range Order in Canary Song

PLoS Comput Biol. 2013;9(5):e1003052. doi: 10.1371/journal.pcbi.1003052. Epub 2013 May 2.

Jeffrey E. Markowitz
Department of Cognitive and Neural Systems, Boston University, Boston, Massachusetts, United States of America
Jeffrey E. Markowitz, Timothy J. Gardner
Center of Excellence for Learning in Education, Science and Technology, Boston, Massachusetts, United States of America
Elizabeth Ivie, Laura Kligler, Timothy J. Gardner
Department of Biology, Boston University, Boston, Massachusetts, United States of America

Bird songs range in form from the simple notes of a Chipping Sparrow to the rich performance of the nightingale. Non-adjacent correlations can be found in the syntax of some birdsongs, indicating that the choice of what to sing next is determined not only by the current syllable, but also by previous syllables sung. Here we examine the song of the domesticated canary, a complex singer whose song consists of syllables, grouped into phrases that are arranged in flexible sequences. Phrases are defined by a fundamental time-scale that is independent of the underlying syllable duration. We show that the ordering of phrases is governed by long-range rules: the choice of what phrase to sing next in a given context depends on the history of the song, and for some syllables, highly specific rules produce correlations in song over timescales of up to ten seconds. The neural basis of these long-range correlations may provide insight into how complex behaviors are assembled from more elementary, stereotyped modules.

Author Summary
Bird songs range in form from the simple notes of a Chipping Sparrow to the complex repertoire of the nightingale. Recent studies suggest that bird songs may contain non-adjacent dependencies where the choice of what to sing next depends on the history of what has already been produced. However, the complexity of these rules has not been examined statistically for the most elaborate avian singers. Here we show that one complex singer—the domesticated canary—produces a song that is strongly influenced by long-range rules. The choice of how long to repeat a given note or which note to choose next depends on the history of the song, and these dependencies span intervals of time much longer than previously assumed for birdsong. Like most forms of human music, the songs of canaries contain patterns expressed over long timescales, governed by rules that apply to multiple levels of a temporal hierarchy. This vocal complexity provides a valuable model to examine how ordered behaviors are assembled from more elementary neural components in a relatively simple neural circuit.

Example Figure
FIGURE 1: Sonograms show a relationship between phrase duration, the context of a phrase, and future choices.
Phrases consist of repetitions of elementary units—the syllables. Distinct phrase types are indicated by colored bars beneath each sonogram. On the right side of each sonogram is a “barcode” summary of all occurrences of the phrases shown in the sonograms. The phrases before (left) and after (right) the gray phrase are color-coded by syllable identity, and the length of the bars in each row indicates duration of the phrase. A square flanks each barcode to indicate the scale, with the width corresponding to 2 seconds and the height to 20 trials. A, A case where the duration of a phrase predicts the future path—the barcode is sorted by duration of the black phrase. Short black bars on the bottom of the barcode typically lead to blue, while long black bars at the top typically lead to green. B, A case where the identity of the starting phrase (red, yellow, or purple) determines which phrase type comes after the black/gray phrase (green or magenta for example.) The barcode in this panel is sorted by the phrase that comes before the black/gray phrase.

Tuesday, 18 March 2014

Research article shows the importance of female song evolution in songbirds - Nature Communications

Female song is widespread and ancestral in songbirds
NATURE COMMUNICATIONS | 5:3379 | DOI: 10.1038/ncomms4379
Karan J. Odom 1
Michelle L. Hall 2
Katharina Riebel 3
Kevin E. Omland 1
Naomi E. Langmore 4
1: Department of Biological Sciences, University of Maryland, Baltimore County, Baltimore, Maryland 21250, USA. 
2: Department of Zoology, University of Melbourne, Melbourne, Victoria 3010, Australia. 
3: Institute of Biology (IBL), Leiden University, 2333 BE Leiden, The Netherlands. 
4: Research School of Biology, The Australian National University, Acton, ACT 0200, Australia. 
Correspondence and requests for materials should be addressed to K.J.O.

Bird song has historically been considered an almost exclusively male trait, an observation fundamental to the formulation of Darwin’s theory of sexual selection. Like other male ornaments, song is used by male songbirds to attract females and compete with rivals. Thus, bird song has become a textbook example of the power of sexual selection to lead to extreme neurological and behavioural sex differences. Here we present an extensive survey and ancestral state reconstruction of female song across songbirds showing that female song is present in 71% of surveyed species including 32 families, and that females sang in the common ancestor of modern songbirds. Our results reverse classical assumptions about the evolution of song and sex differences in birds. The challenge now is to identify whether sexual selection alone or broader processes, such as social or natural selection, best explain the evolution of elaborate traits in both sexes.

This short communication paper provides evidence to explain the author's hypothesis that evolution by sexual selection is not restricted to the male line but that female songbirds play a significant role too. This hypothesis is based on two observations: (1) the majority of songbird biodiversity exists in tropical regions, where both females and males of many species sing; (2) female song is widespread in Australasia, the region from which songbirds are thought to have originated. It is a commonly held understanding that females select a partner based on their 'fitness' and thus males would develop more elaborate song repertoires. The authors even quote from Darwin's 1859 book 'On the Origin of Species':

‘... female birds, by selecting, during thousands of generations, the most melodious or beautiful males, according to their standard of beauty, might produce a marked effect’

By way of contrast the authors aimed to provide a quantitative test of their hypothesis, by surveying the occurrence and distribution of female-specific song, and then using ancestral state reconstruction to examine the likelihood that females sang in the ancestor of all songbirds. 

The authors investigated the presence of female song in 1,141 songbird species, and were able to score 323 of these species. This represented 34 of the short-list of 44 songbird families examined from the approximate 112 total species list, after removing the Passerida. Although these are the most specious Parvorder of songbirds (3,822 of 5,023 songbirds) they were not useful in determining the ancestral lines as they were the most recent radiation.

This survey showed that female song is present in 71% of the selected species providing strong evidence that female song is globally and phylogenetically widespread.
Superimposing these data onto that of an evolutionary tree compiled from DNA sequence data (Pubmed Link), the authors then calculated that female song was most likely to have been present in the ancestral state. This challenged the view that sexual dimorphism in song production arises primarily as a result of sexual selection. 
A pictorial representation of the ancestral data is shown in Figure 1 below.

Figure 1

The tree (a) includes all species for which we could unambiguously score female song as present or absent (323/1,141 species from 34/44 songbird families). Female song was present in 229 species (32 families; red terminal nodes) and female song was absent in 94 species (19 families; blue terminal nodes). The pie chart in the centre shows that female song is reconstructed as present (red) in the common ancestor of modern songbirds (92% maximum-likelihood probability strongly supported by a likelihood decision threshold of 2.0). Pictures show females of the following species with female song from families throughout the phylogeny; (b) superb lyrebird (Menura novaehollandiae; figure reproduced with permission from V. Dunis), (c) purple-crowned fairywren (Malurus coronatus; figure reproduced with permission from M. Hall), (d) brown thornbill (Acanthiza pusilla; figure reproduced with permission from J.J. Harrison), (e) scarlet robin (Petroica boodang; figure reproduced with permission from K. Odom), (f) white-eyed vireo (Vireo griseus; figure reproduced with permission from F. Jacobsen), (g) grey butcherbird (Cracticus torquatus; figure reproduced with permission from A. Kearns), (h) tropical boubou (Laniarius aethiopicus; figure reproduced with permission from J. Friedman), (i) loggerhead shrike (Lanius ludovicianus; figure reproduced with permission from F. Jacobsen), (j) magpie-lark (Grallina cyanoleuca; figure reproduced with permission from M. Hall), (k) curl-crested manucode (Manucodia comrii; figure reproduced with permission from T. Laman).

Monday, 17 March 2014

Journal of Avian Biology - 'Seabird' Virtual Issue March 2014: Abstract Listing

Introduction from the Editors
"With this Virtual Issue of Journal of Avian Biology we wish to highlight some of the many papers focusing on Seabird biology published by the Journal. The issue is especially compiled for the International Seabird Group Conference in Oxford in March 2014 and represent the diverse and complex biology of this fascinating group of birds. Journal of Avian Biology has a strong tradition of publishing papers on all aspects of seabird biology and we hope that you will find this thematic virtual issue especially interesting. All the papers are freely available for everyone to enjoy."

Below are the links, titles, authors, and abstracts of the free access papers.

The individual counts: within sex differences in foraging strategies are as important as sex-specific differences in masked boobies Sula dactylatra
Julia Sommerfeld, Akiko Kato, Yan Ropert-Coudert, Stefan Garthe, Mark A. Hindell

Understanding how animals allocate their foraging time is a central question in behavioural ecology. Intrinsic factors, such as body mass and size differences between sexes or species, influence animals’ foraging behaviour, but studies investigating the effects of individual differences in body mass and size within the same sex are scarce. We investigated this in chick-rearing masked boobies Sula dactylatra, a species with reversed sexual dimorphism, through the simultaneous deployment of GPS and depth-acceleration loggers to obtain information on foraging movements and activity patterns. Heavier females performed shorter trips closer to the colony than lighter females. During these shorter trips, heavier females spent higher proportions of their flight time flapping and less time resting on the water than lighter females did during longer trips. In contrast, body mass did not affect trip duration of males, however heavier males spent less time flapping and more time resting on the water than lighter males. This may occur as a result of higher flight costs associated with body mass and allow conservation of energy during locomotion. Body size (i.e. wing length) had no effect on any of the foraging parameters. Dive depths and dive rates (dives h−1) were not affected by body mass, but females dived significantly deeper than males, suggesting that other factors are important. Other studies demonstrated that females are the parent in charge of provisioning the chick, and maintain a flexible investment under regulation of their own body mass. Variation in trip length therefore seems to be triggered by body condition in females, but not in males. Consequently, shorter trips are presumably used to provision the chick, while longer trips are for self-maintenance. Our findings underline the importance of accounting for the effects of body mass differences within the same sex, if sex-specific foraging parameters in dimorphic species are being investigated.
Networks of prey specialization in an Arctic monomorphic seabird
Jennifer F. Provencher, Kyle H. Elliott, Anthony J. Gaston, Birgit M. Braune

Generalist predator populations are sometimes made up of individuals that specialize on particular prey items. To examine specialization in thick-billed murres Uria lomvia during self-feeding we obtained stomach contents and muscle stable isotope values for 213 birds feeding close to five colonies in the Canadian Arctic. Adults were less specialized during self-feeding than during chick-provisioning. Nonetheless, particular specialists clustered together within the foraging network. While sexes showed similar levels of specialization, individuals of the same sex clustered together within the foraging network. The significant degree of clustering regardless of sex showed that individuals specializing on one prey item tend to also specialize on another, although network topology varied from colony to colony. Adult muscle stable isotope values correlated with the stable isotope values of the prey found in stomachs, at least at the one colony with relevant prey data, suggesting that specializations are maintained over time. Degree of specialization increased with niche width across the five colonies, but similarity in gastro-intestinal and bill morphology was independent of dietary similarity. Thus, although individual specialization is thought to play a key role in sympatric speciation through trophic specialization, we found no support for an association between morphology and foraging patterns in our species. We conclude that self-feeding murres show clustered dietary specialization, and that specialization is highest where diet is most diverse.
Movements and activities of male black-tailed gulls in breeding and sabbatical years
Kentaro Kazama, Kazuhiko Hirata, Takashi Yamamoto, Hiroshi Hashimoto, Akinori Takahashi, Yasuaki Niizuma, Philip N. Trathan, Yutaka Watanuki

Long-lived animals sometimes skip one or more breeding seasons; however, little is known about their movements and activities during such ‘sabbatical’ periods. Here we present novel data on year-round movements and activities of two male black-tailed gulls Larus crassirostris during a sabbatical year. We compare the data with those in a year when they bred and with those of two other breeding males. The year-round migration routes of two sabbatical males were consistent with those of the breeding males: they returned to the breeding area but did not visit the colony in the sabbatical year. They landed more frequently on water (a potential index of foraging effort) during the non-breeding autumn and winter prior to the sabbatical year than before breeding. Sabbatical gulls may forage more intensively to recover body condition immediately after breeding.
Colouration in Atlantic puffins and blacklegged kittiwakes: monochromatism and links to body condition in both sexes
Claire Doutrelant, Arnaud Grégoire, Doris Gomez, Vincent Staszewski, Emilie Arnoux, Torkild Tveraa, Bruno Faivre, Thierry Boulinier

Sexual dimorphism is widely used as an indirect measure of the intensity of sexual selection. It is also a way to evaluate whether different selective pressures act on males and females. Dichromatism, defined as a difference in colouration between males and females, may for instance result from selection for crypsis in females and selection for conspicuousness in males. Here, we conducted a study to investigate whether differential sexual selective pressures might act on the colour traits of two colonial seabird species, the Atlantic puffin Fratercula artica and the black-legged kittiwake Rissa tricactyla. First, we used spectrophotometry and visual modelling to determine whether these presumed monomorphic birds are really monochromatic from an avian perspective (birds and humans have a different vision). Second, we estimated whether some of their colourations have the potential to be sexually or socially selected by determining whether these colourations were related to body condition in males and females, and whether the yellow, orange and red colourations may contain carotenoid pigments. Our results indicated that both species were fully monochromatic from an avian perspective. Moreover, our preliminary analyses suggested that the yellow, orange and red colours of these birds contained carotenoids. Lastly, some indices of colouration were positively linked to estimates of condition. Birds in better condition had redder gape (both species) and bill (puffins). In puffins, the relation between condition and gape colouration was significantly stronger in females than males. By contrast, the size of the gape rosette was larger in males than females. The positive links we found between colour indices and condition, together with the absence of sexual dichromatism, suggest that mutual sexual selection may act in these two species.
Chronic stress in infancy fails to affect body size and immune response of adult female blue-footed boobies or their offspring
María Cristina Carmona-Isunza, Alejandra Núñez-de la Mora, Hugh Drummond

Experiments on birds, fish and mammals have shown that adverse conditions during infancy can produce diverse long-term and delayed deficits during adulthood, prejudicing both the individual and its offspring. Natural selection should prepare animals to cope with adversity of the type, magnitude and timing that commonly occur in their natural habitat, but very little is known about such evolved developmental buffering against natural ‘poor starts’ in life. In two-chick broods of the blue-footed booby Sula nebouxii, the junior (younger) chick usually experiences aggressive subordination, reduced nutrition and growth and elevated circulating corticosterone. To test whether this poor start produces long-term, delayed or intergenerational deficits in body size, body condition or cell-mediated immune response, we measured 3–8 yr old female breeders banded as chicks, and their infant offspring. Results failed to support our predictions. Compared to former seniors and former singletons (solitary nestlings), former juniors showed no deficit in cell-mediated immune response at any age. They showed an 8.04% deficit in body condition at age 4–6 yr but this deficit disappeared completely by age 7–8 yr. Furthermore, their offspring showed no deficits in body size, body condition or immune response. Junior chicks are affected by their poor start, but their developmental resilience, also confirmed by studies of post-fledging survivorship, recruitment, natal dispersal, aggressive nest defense and reproduction, is evidence of evolved developmental buffering against predictable adversity during infancy.
Energetic consequences of contrasting winter migratory strategies in a sympatric Arctic seabird duet
Jérôme Fort, Harald Steen, Hallvard Strøm, Yann Tremblay, Eirik Grønningsæter, Emeline Pettex, Warren P. Porter, David Grémillet

At the onset of winter, warm-blooded animals inhabiting seasonal environments may remain resident and face poorer climatic conditions, or migrate towards more favourable habitats. While the origins and evolution of migratory choices have been extensively studied, their consequences on avian energy balance and winter survival are poorly understood, especially in species difficult to observe such as seabirds. Using miniaturized geolocators, time-depth recorders and a mechanistic model, we investigated the migratory strategies, the activity levels and the energy expenditure of the closely-related, sympatrically breeding Brünnich's guillemots Uria lomvia and common guillemots Uria aalge from Bjørnøya, Svalbard. The two guillemot species from this region present contrasting migratory strategies and wintering quarters: Brünnich's guillemots migrate across the North Atlantic to overwinter off southeast Greenland and Faroe Islands, while common guillemots remain resident in the Barents, the Norwegian and the White Seas. Results show that both species display a marked behavioural plasticity to respond to environmental constraint, notably modulating their foraging effort and diving behaviour. Nevertheless, we provide evidence that the migratory strategy adopted by guillemots can have important consequences for their energy balance. Overall energy expenditure estimated for the non-breeding season is relatively similar between both species, suggesting that both southward migration and high-arctic winter residency are energetically equivalent and suitable strategies. However, we also demonstrate that the migratory strategy adopted by Brünnich's guillemots allows them to have reduced daily energy expenditures during the challenging winter period. We therefore speculate that ‘resident’ common guillemots are more vulnerable than ‘migrating’ Brünnich's guillemots to harsh winter environmental conditions.
Specialization to cold-water upwellings may facilitate gene flow in seabirds: new evidence from the Peruvian pelican Pelecanus thagus (Pelecaniformes: Pelecanidae)
Will S. Jeyasingham, Scott A. Taylor, Carlos B. Zavalaga, Alejandro Simeone, Vicki L. Friesen

Recent research has shown that tropical seabirds specialized to feed on cold water upwellings exhibit low population genetic differentiation and high gene flow across large geographic distances. This pattern is opposite to the general pattern of differentiation reported for tropical seabirds, and led us to hypothesize that specialization to cold-water upwellings facilitates gene flow between colonies. As a test of this hypothesis we characterized population differentiation and gene flow across the range of the Peruvian pelican Pelecanus thagus, an upwelling specialist endemic to the Humboldt Current, using an 838 base pair segment of the mitochondrial control region and seven microsatellite loci. In support of our hypothesis we report genetic panmixia across the geographic range of this species and inferred high gene flow between colonies. The high dispersal propensity of upwelling specialist seabirds (adults and/or juveniles) may reduce loss of genetic diversity during population declines, and increase the ability of these species to colonize new islands.
The population increase of common guillemots Uria aalge on Skomer Island is explained by intrinsic demographic properties
Jessica Meade, Ben J. Hatchwell, Julia L. Blanchard, Tim R. Birkhead

The population of common guillemots Uria aalge on Skomer Island, Wales has been monitored since 1963, and in the last 30 yr has increased at an almost constant rate of 5% yr−1. A previous attempt to model the population based on intrinsic demographic parameters estimated over just five years failed to explain the observed population increase, probably because the estimate of juvenile survival was too low. This raised the possibility that immigration fuelled the population increase. Here we use > 30 yr of detailed field observations to re-estimate key population parameters (productivity, adult survival and juvenile survival) in order to model the population. We show that the observed rate of increase can be explained by these intrinsic parameters, and we therefore conclude that immigration is not necessary to generate the observed population growth.
Rates and consequences of relaying in little auks Alle alle breeding in the High Arctic an experimental study with egg removal
Dariusz Jakubas, Katarzyna Wojczulanis-Jakubas

Most seabirds have a small clutch size. Thus, replacement of a clutch after loss can make important contributions to an individual’s lifetime reproductive success. However, in the condition of short polar summer, relaying propensity may be time-constrained. In this study, we investigated rates and consequences of relaying in a small High Arctic seabird, the little auk Alle alle. We performed an experiment in which we removed the single egg from 20 nests of early-laying breeders. We measured relaying rates, and compared chick body mass and breeding success between the experimental and control nests. Despite the narrow window of the Arctic summer and the closely synchronized breeding, 75% of females produced a replacement egg just 2.7% smaller in volume than the first egg. This indicates that in little auks, the demographic effects of disruptions to breeding attempts (by predators, adverse weather or human activity) may be mitigated to some extent by replacement clutches. However, peak body mass and fledging body mass were lower in the experimental than the control chicks. This effect was rather a consequence of late hatching – chicks from replacement clutches followed seasonal decline in peak body mass and fledging mass. Finally, breeding success and chick survival up to 20 d in the experimental nests were respectively 34 and 37% lower than in the control nests. Thus, the quality and post-fledging survival of chicks from the replacement clutches were probably lower compared to the chicks hatched from the first-laid eggs.
Predator–prey interactions between the South Polar skua Catharacta maccormicki and Antarctic tern Sterna vittata
Karel Weidinger, Václav Pavel

Antarctic terns have to co-exist in a limited space with their major nest predator, the skuas. We conducted artificial nest experiments to evaluate the roles of parental activity, nest location and nest and egg crypsis in this simple predator–prey system. Predation on artificial (inactive) nests was higher in traditional nesting sites than in sites previously not occupied by terns, which suggests that skuas memorized past tern breeding sites. Predation on artificial nests in inactive colonies was higher than in active (defended) colonies. Parental defense reduced predation in colonies to the level observed in artificial nests placed away from colonies. This suggests that communal defense can balance the costs of attracting predators to active colonies. Within colonies, predation was marginally higher on experimental eggs put in real nests than on bare ground. Although it seems that the presence of a nest is costly in terms of increased predation, reductions in nest size might be constrained by the need for protective nest structures and/or balanced by opposing selection on nest size. Predation did not differ markedly between artificial (quail) and real tern eggs. A simultaneous prey choice experiment showed that the observed predation rates reflected egg/nest detectability, rather than discrimination of egg types. In summary, nesting terns probably cannot avoid being detected, and they cannot defend their nest by attending them. Yet, by temporarily leaving the nest, they can defend it through communal predator mobbing, and at the same time, they can benefit from crypsis of unattended nest and eggs.
Evidence for strong assortative mating, limited gene flow, and strong differentiation across the blue-footed/Peruvian booby hybrid zone in northern Peru
Scott A. Taylor, David J. Anderson, Carlos B. Zavalaga and, Vicki L. Friesen

Hybrid zones represent natural laboratories in which the processes of divergence and genetic isolation can be examined. The generation and maintenance of a hybrid zone requires mispairing and successful reproduction between organisms that differ in one or more heritable traits. Understanding the dynamics of hybridization between two species requires an understanding of the extent to which they have diverged genetically, the frequency of misparing and hybrid production, and the extent of introgression. Three hundred and twenty one blue-footed Sula nebouxii and Peruvian S. variegata boobies from the eastern tropical Pacific Ocean were analyzed using 19 putatively neutral genetic markers to evaluate interspecific differentiation, to classify morphological hybrids using Bayesian assignments, and to characterize hybridization using cline theory and Bayesian assignments. The species were well differentiated at mitochondrial and nuclear microsatellites, the hybrid zone was bimodal (contained a high frequency of each parental species but a low frequency of hybrids), and morphologically intermediate individuals were most likely F1 hybrids resulting from mating between female Peruvian boobies and male blue-footed boobies. Clines in allele frequency could be constrained to share a common geographic centre but could not be constrained to share a common width. Peruvian and blue-footed boobies hybridize infrequently, potentially due to strong premating reproductive isolation; however, backcrossing appears to facilitate introgression from blue-footed to Peruvian boobies in this hybrid system.
Divergent diving behavior during short and long trips of a bimodal forager, the little auk Alle alle
Zachary W. Brown, Jorg Welcker, Ann M. A. Harding, Wojciech Walkusz, Nina J. Karnovsky

The purpose of this study was to characterize for the first time seabird diving behavior during bimodal foraging. Little auks Alle alle, small zooplanktivorous Alcids of the High Arctic, have recently been shown to make foraging trips of short and long duration. Because short (ST) and long trips (LT) are thought to occur in different locations and serve different purposes (chick- and self-feeding, respectively) we hypothesized that foraging differences would be apparent, both in terms of water temperature and diving characteristics. Using Time Depth Recorders (TDRs), we tested this hypothesis at three colonies along the Greenland Sea with contrasting oceanographic conditions. We found that diving behavior generally differed between ST and LT. However, the magnitude of the disparity in diving characteristics depended on local foraging conditions. At the study site where conditions were favorable, diving behavior differed only to a small degree between LT and ST. Together with a lack of difference in diving depth and ocean temperature, this indicates that these birds did not increase their foraging effort during ST nor did they travel long distances to seek out more profitable prey. In contrast, where local foraging conditions were poor, birds increased their diving effort substantially to collect a chick meal during ST as indicated by longer, more U-shaped dives with slower ascent rates and shorter resting times (post-dive intervals and extended surface pauses). In addition, large differences in diving depth and ocean temperature indicate that birds forage on different prey species and utilize different foraging areas during LT, which may be up to 200 km away from the colony. Continued warming and deteriorating near-colony foraging conditions may have energetic consequences for little auks breeding in the eastern Greenland Sea.
Seasonal variation in pre-fledging survival of lesser scaup Aythya affinis: hatch date effects depend on maternal body mass
Kirsty E. B. Gurney, Robert G. Clark, Stuart M. Slattery

Among temperate-breeding birds, offspring survival and reproductive success are often inversely related to timing of breeding. The mechanisms that produce seasonal declines in offspring survival are not fully understood but may be related to temporal changes in parental quality, environmental quality, or both. We analyzed data for lesser scaup Aythya affinis to evaluate hypothesized effects of parental quality and date on pre-fledging survival. Maternal quality, as indexed by body mass, did not have an independent effect on offspring survival in this species. Maternal body mass did not decline seasonally and did not have an independent effect on duckling survival. Although we did not detect an independent effect of hatch date on duckling survival, duckling survival declined seasonally for broods raised by lightweight females, indicating an interactive effect of maternal mass and date. We hypothesize that this interaction may be driven by seasonally declining food resources coupled with the influence of female condition on the ability to monopolize food resources or remain attentive to the brood. We also tested morphological predictions of the date hypothesis by examining physical characteristics of ducklings. When corrected for age and size, late-hatched ducklings tended to have marginally larger digestive systems and smaller leg muscles than did early-hatched birds. Abundances of intestinal parasites acquired through diet decreased marginally in late-hatched ducklings. Results for digestive system and parasite infection patterns suggested that later-hatched broods may shift diets, consistent with a contribution of environmental factors to seasonal variation in offspring survival. Taken together, our results suggest that both female attributes and environmental conditions may influence seasonal patterns of offspring survival in this species.