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Monday, 23 June 2014

Bird research this week on PubMed: June 2014 Week 3

PubMed listing for 'bird' OR 'songbird' excluding references to influenza and flu - June 2014 Week 3

1. Ecology. 2014 Apr;95(4):1065-74.

Cascading effects of insectivorous birds and bats in tropical coffee plantations.

Karp DS, Daily GC.


The loss of apex predators is known to have reverberating consequences for ecosystems, but how changes in broader predator assemblages affect vital ecosystem functions and services is largely unknown. Predators and their prey form complex interaction networks, in which predators consume not only herbivores but also other predators. Resolving these interactions will be essential for predicting changes in many important ecosystem functions, such as the control of damaging crop pests. Here, we examine how birds, bats, and arthropods interact to determine herbivorous arthropod abundance and leaf damage in Costa Rican coffee plantations. In an exclosure experiment, we found that birds and bats reduced non-flying arthropod abundance by -35% and -25%, respectively. In contrast, birds and bats increased the abundance of flying arthropods, probably by consuming spiders. The frequency of this intraguild predation differed between birds and bats, with cascading consequences for coffee shrubs. Excluding birds caused a greater increase in herbivorous arthropod abundance than excluding bats, leading to increased coffee leaf damage. Excluding bats caused an increase in spiders and other predatory arthropods, increasing the ratio of predators to herbivores in the arthropod community. Bats, therefore, did not provide benefits to coffee plants. Leaf damage on coffee was low, and probably did not affect coffee yields. Bird-mediated control of herbivores, however, may aid coffee shrubs in the long-term by preventing pest outbreaks. Regardless, our results demonstrate how complex, cascading interactions between predators and herbivores may impact plants and people.
PMID: 24933824 [PubMed - in process]
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2. Ecology. 2014 Apr;95(4):1033-44.

Experimentally elevated levels of testosterone at independence reduce fitness in a territorial bird.

Martínez-Padilla J, Pérez-Rodríguez L, Mougeot F, Ludwig SC, Redpath SM.


Environmental conditions and individual strategies in early life may have a profound effect on fitness. A critical moment in the life of an organism occurs when an individual reaches independence and stops receiving benefits from its relatives. Understanding the consequences of individual strategies at the time of independence requires quantification of their fitness effects. We explored this period in the Red Grouse (Lagopus lagopus scoticus). In this system, testosterone and parasite (Trichostrongylus tenuis) levels are known to influence survival and reproduction, the two key components of individual fitness. We experimentally and simultaneously manipulated testosterone and parasites at three levels (high, intermediate, and control levels for both factors) in 195 young males in five populations using a factorial experimental design. We explored the effects of our treatments on fitness by monitoring reproduction and survival throughout the life of all males and estimating lambda(ind), a rate-sensitive index of fitness. Parasite challenges increased the number of worms with a time lag, as previously found. However, we did not find significant effects of parasite manipulations on fitness, possibly because parasite abundance did not increase to harmful levels. Our hormone manipulation was successful at increasing testosterone at three different levels. Such increases in hormone levels decreased overall fitness. This was caused by reduced offspring production in the first breeding attempt rather than by any effect of the treatment on bird survival. Our results highlight that investing in high testosterone levels at independence, a strategy that might enhance short-term recruitment probability in territorial species such as Red Grouse, has a fitness cost, and can influence the resolution of the trade-off between reproduction and survival later in life.
PMID: 24933821 [PubMed - in process]
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3. Proc Natl Acad Sci U S A. 2014 Apr 22;111(16):6063-8. doi: 10.1073/pnas.1317087111. Epub 2014 Apr 7.

Evidence for a causal inverse model in an avian cortico-basal ganglia circuit.

Giret N1, Kornfeld J, Ganguli S, Hahnloser RH.Author information:
1Institute of Neuroinformatics and Neuroscience Center Zurich, University of Zurich and ETH Zurich, 8057 Zurich, Switzerland.


Learning by imitation is fundamental to both communication and social behavior and requires the conversion of complex, nonlinear sensory codes for perception into similarly complex motor codes for generating action. To understand the neural substrates underlying this conversion, we study sensorimotor transformations in songbird cortical output neurons of a basal-ganglia pathway involved in song learning. Despite the complexity of sensory and motor codes, we find a simple, temporally specific, causal correspondence between them. Sensory neural responses to song playback mirror motor-related activity recorded during singing, with a temporal offset of roughly 40 ms, in agreement with short feedback loop delays estimated using electrical and auditory stimulation. Such matching of mirroring offsets and loop delays is consistent with a recent Hebbian theory of motor learning and suggests that cortico-basal ganglia pathways could support motor control via causal inverse models that can invert the rich correspondence between motor exploration and sensory feedback.
PMCID: PMC4000851 [Available on 2014/10/22]
PMID: 24711417 [PubMed - indexed for MEDLINE]
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4. Proc Natl Acad Sci U S A. 2014 Apr 22;111(16):6109-14. doi: 10.1073/pnas.1320957111. Epub 2014 Apr 7.

Effects of land use on bird populations and pest control services on coffee farms.

Railsback SF1, Johnson MD.Author information:
1Department of Mathematics and Department of Wildlife, Humboldt State University, Arcata, CA 95521.


Global increases in both agriculture and biodiversity awareness raise a key question: Should cropland and biodiversity habitat be separated, or integrated in mixed land uses? Ecosystem services by wildlife make this question more complex. For example, birds benefit agriculture by preying on pest insects, but other habitat is needed to maintain the birds. Resulting land use questions include what areas and arrangements of habitat support sufficient birds to control pests, whether this pest control offsets the reduced cropland, and the comparative benefits of "land sharing" (i.e., mixed cropland and habitat) vs. "land sparing" (i.e., separate areas of intensive agriculture and habitat). Such questions are difficult to answer using field studies alone, so we use a simulation model of Jamaican coffee farms, where songbirds suppress the coffee berry borer (CBB). Simulated birds select habitat and prey in five habitat types: intact forest, trees (including forest fragments), shade coffee, sun coffee, and unsuitable habitat. The trees habitat type appears to be especially important, providing efficient foraging and roosting sites near coffee plots. Small areas of trees (but not forest alone) could support a sufficient number of birds to suppress CBB in sun coffee; the degree to which trees are dispersed within coffee had little effect. In simulations without trees, shade coffee supported sufficient birds to offset its lower yield. High areas of both trees and shade coffee reduced pest control because CBB was less often profitable prey. Because of the pest control service provided by birds, land sharing was predicted to be more beneficial than land sparing in this system.
PMCID: PMC4000777 [Available on 2014/10/22]
PMID: 24711377 [PubMed - indexed for MEDLINE]
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5. Bull Environ Contam Toxicol. 2014 Apr;92(4):433-9. doi: 10.1007/s00128-014-1238-1. Epub 2014 Mar 2.

Comparison of the metal concentrations in organs of two bird species from western of Iran.

Mansouri B1, Majnoni F.Author information:
1Young Researchers and Elite Club, Kermanshah Branch, Islamic Azad University, Kermanshah, Iran,


This study was conducted to measure the concentration of several elements (Cd, Pb, Cu, and Zn) in organs of Coot, Fulica atra, and Mallard, Anas platyrhynchos, in order to: (1) determine the significant between metal concentrations in different organs (kidney, liver, pectoral muscle, and feather), (2) to evaluate species differences in metal exposure and accumulation, and (3) to study gender-related trends in metal accumulation. The metal concentrations in organs of F. atra and A. platyrhynchos decreased in the following order: Zn > Cu > Pb > Cd. These results revealed that there were no significant differences between males and females except for Cu in liver and feather, and Pb in kidney.
PMID: 24584267 [PubMed - indexed for MEDLINE]
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7. Environ Microbiol. 2014 Apr;16(4):1081-9. doi: 10.1111/1462-2920.12332. Epub 2013 Dec 5.

Are the specialized bird ticks, Ixodes arboricola and I. frontalis, competent vectors for Borrelia burgdorferi sensu lato?

Heylen D1, Sprong H, van Oers K, Fonville M, Leirs H, Matthysen E.Author information:
1Department of Biology, University of Antwerp, Evolutionary Ecology Group, Belgium.


Our study tested whether two European bird-specialized ticks, Ixodes arboricola and I. frontalis, can act as vectors in the transmission cycles of Borrelia burgdorferi s.l. The ticks have contrasting ecologies but share songbird hosts (such as the great tit, Parus major) with the generalist I. ricinus which may therefore act as a bridging vector. In the first phase of the experiment, we obtained Borrelia-infected ornithophilic nymphs by exposing larvae to great tits that had previously been exposed to I. ricinus nymphs carrying a community of genospecies (Borrelia garinii, valaisiana, afzelii, burgdorferi s.s., spielmanii). Skin samples showed that birds selectively amplified B. garinii and B. valaisiana. The spirochetes were transmitted to the ornithophilic ticks and survived moulting, leading to infection rates of 16% and 27% in nymphs of I. arboricola and I. frontalis respectively. In the second phase, pathogen-free great tits were exposed to the Borrelia-infected ornithophilic nymphs. None of these ticks were able to infect the birds, as indicated by the tissue samples. Analysis of xenodiagnostic I. ricinus larvae found no evidence for co-feeding or systemic transmission of B. burgdorferi s.l. These outcomes do not support the occurrence of enzootic cycles of Borrelia burgdorferi s.l. involving songbirds and their specialized ornithophilic ticks.
© 2013 Society for Applied Microbiology and John Wiley & Sons Ltd.
PMID: 24237635 [PubMed - indexed for MEDLINE]
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