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Tuesday, 21 January 2014

Add multi-vitamins to the seeds on your bird-table, if you want the Great Tits to be healthy and look their best, according to the latest research from Switzerland.

Research Article title:
Differential effects of vitamins E and C and carotenoids on growth, resistance to oxidative stress, fledging success and plumage colouration in wild great tits.

Viviana Marri and Heinz Richner
Evolutionary Ecology Lab, Institute of Ecology and Evolution, University of Bern, Baltzerstrasse 6, 3012 Bern, Switzerland

Journal of Experimental Biology jeb.096826; First posted online January 16, 2014


The goal of this research paper was to understand the impact of vitamins and carotenoids on levels of oxidative stress in the Great Tit (Parus major). Oxidative stress is the imbalance between antioxidants and the production of reactive species (such as free-radicals produced by metabolic processes especially during significant growth phases) which cause damage to lipids, proteins and DNA. Antioxidants, like vitamins and carotenoids, can limit oxidative damage and can therefore regulate the trade-off between growth, which is a period of high reactive species production, and self-maintenance. We are all aware of the 'superfoods' that we as humans are told we must eat due to their antioxidant, anti-aging properties.

The experiment was carried out during spring 2011 in a free-ranging population of Great Tits, breeding in nest-boxes in the Forst and Bremgartenwald forests, near Bern, Switzerland from the beginning of the breeding season to determine the day of the start of incubation and the day of hatching (day 0).
Nest-boxes were randomly assigned to four treatments: control group (N=23), carotenoid group (N=23), vitamin group (N=25), combined carotenoid plus vitamin group (N=27). The nestlings were given one larva of Calliphora spp on days 3, 5, 7 after hatching. This larva was coated with corn oil for control nestlings and with either carotenoids (lutein and zeaxanthin), vitamins (E and C), or carotenoids plus vitamins, for treated nestlings.
On day 3 post-hatch they measured nestling body mass. On day 8 and 14 post-hatch, they measured body mass, and additionally on day 8 they took a blood sample from the brachial vein for analysis of oxidative stress.
On day 15 post-hatch they collected six feathers from 2 patches on both sides of the chest, from each nestling, and stored them in small plastics bags kept in the dark before taking spectrometric measurements for feather reflectance.

They found that an increased availability of vitamins enhanced growth, antioxidant capacity and strongly improved fledging success. In contrast, carotenoid supplementation did not affect any of these fitness-related traits and, when supplemented together with vitamins, did not show any synergistic effects on the expression of a carotenoid-based signal. Vitamins, but not carotenoids, increased carotenoid-based colouration over the breeding season. The results thus showed that vitamins have major effects on several fitness-related traits and suggest that vitamins may play a central role in the trade-off between growth and self-maintenance.

Figure 1. Predicted square root transformed antioxidant capacity (minutes) in relation to vitamin treatment. Horizontal lines in box are 25th, 50th and 75th percentiles; whiskers show the maximum and minimum value. 

Figure 2. Predicted change in body mass, measured in grams, from day 8 to 14 in relation to vitamin treatment. Horizontal lines in box are 25th, 50th and 75th percentiles; whiskers show the maximum and minimum value. 

Figure 3. SWS ratio (an index of chromatic reflectance) in relation to hatching date in nestlings of the four experimental groups. The lines are the linear regression lines.

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