The Dehesa is a cleared mixed forest of oak and ash trees, managed for cattle grazing. We have 250 nests boxes in a Dehesa forest, where starlings build their nests. We have been following a population of spotless starlings in central Spain, 40 km north of Madrid for the last 14 years.
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In addition, we wanted to know how the mating system and the presence of parasitic offspring modulated the potential costs of reproduction Tracking A Population Of Spotless Starlings We expected to find that if reproduction is costly, a female making a big investment in the first brood will pay a cost in the second brood (by not reproducing or decreasing investment), or the next year. Starlings can lay up to two clutches in spring, one in April, when resources are more abundant, and one in late May – early June, when not all females manage to reproduce, and resources are less abundant. In this study, we wanted to know whether reproduction was costly for spotless starlings. Male and female Spotless Starlings (credit: Raquel Monclús) Spotless starlings are also very interesting because some females do not defend a nest, and instead lay their eggs in others’ nests, leaving the costs of incubating and raising the extra offspring to the foster parents. Therefore, we would expect to find differences in costs of reproduction depending on the social mating system in which a female is engaged. However, in some species, such as the spotless starling, a common passerine bird, males might mate with more than one female at a time, and, therefore, males divide their care between two nests, with a primary female, who receives more help, and a secondary female, that receives the remains. Many bird species form monogamous pairs during the breeding season. Moreover, the social environment where an individual lives might also increase or decrease the costs of raising offspring. Some individuals are better able to acquire resources, such as food, than others. In general, whether we might expect to find a cost in future reproduction or survival depends on the availability of resources, but also on the quality of the individual.
In a more dramatic scenario, if it uses too many resources to produce offspring, it might not have enough resources to survive the winter. If an animal (or a plant) that lives several years invests a lot in one reproductive event, it might not have the resources to invest a lot in the following reproductive events. For instance, if animals (or plants) use many resources in producing offspring, they cannot use the same resources to grow or to repair their cells. We discuss possible roles of maternal effects, parasites, immunity and nestling growth in explaining these experimental effects.One of the principles of behavioral ecology is that resources are limited, and thus, allocation decisions have to be made to make ends meet. This relationship could be partially mediated by the antimicrobial and/or antiparasitic properties of nest materials or by sexual signalling processes. Taken together, these results suggest a direct link between nest material composition and nestling telomere length and dynamics.
#SPOTLESS STARLING SKIN#
Moreover, prevalence of staphylococci on the skin of 8-day-old nestlings was negatively related to telomere lengths of fledglings. Feather pigmentation also did not affect telomere length or attrition in general, but did in interaction with location: in Hueneja, the experimental addition of unpigmented feathers resulted in nestlings with longer telomeres and lower attrition rates. The addition of plants did not affect nestling telomeres in general, but did in interaction with location: in Hueneja, the experimental addition of green plants resulted in longer telomeres. After correcting for these effects, the addition of feathers resulted in higher rates of telomere attrition. Telomere length and attrition largely depended on population identity and hatching date. In a full-factorial experiment, we explored these effects in two different populations, together with the potential effects of hatching date, ectoparasitism, bacterial environment and nestling growth. The aim of our study was to experimentally assess their influence on nestlings' telomere length and attrition, which are good predictors of their survival prospects. In spotless starlings, Sturnus unicolor, green plants and feathers are known nest materials with such functions. They can modify the bacterial and parasitic environment of the nest, and can influence parental investment through sexual signalling processes.
Nest materials used by animals can have profound effects on developing offspring.
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