Adopting Behavior and Breeding Biology of Avocets: Benefits of Large Broods for Good Parents?

Lengyel, Szabolcs (2001) Adopting Behavior and Breeding Biology of Avocets: Benefits of Large Broods for Good Parents? PhD thesis, University of Nevada.


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Supervisor name: Tracy, Richard
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Alloparental care, in which adults provide care for young that are not genetically related to them, is widespread in birds and mammals. Caring for unrelated young appears to decrease the fitness of adopters and thus the behavior is difficult to explain based on classic evolutionary theory. I studied the evolutionary significance of adoption in avocets (Recurvirostra avosetta), a large-sized shorebird breeding on alkaline lakes in Hungary between 1998 and 2000. Thirteen percent of the chicks were adopted chicks and 21% of the avocet families contained adopted young. Most adopted chicks left their own family to gain adoption elsewhere, whereas some chicks were left behind by their parents. More chicks survived in larger broods than in smaller ones. The survival of chicks that left their own family and their siblings remaining in the brood did not differ, whereas chicks that were left behind reached the same survival as their siblings in the natal brood. The quality of the adults was also important, because pairs that later adopted chicks laid their eggs earlier, occupied better territories and fledged more young than did non-adopting pairs. Experimentally enlarged broods fledged more young than did modified or control broods in high predation sites. Incubating experimentally enlarged clutches of eggs required higher energy expenditure by parents. Therefore, I concluded that adoption may be a means to increase the size of the brood for certain, high-quality pairs without incurring the costs of producing and incubating more eggs. Adoption appears to provide fitness benefits to the adopting parents via an increase in brood size. However, adoption is not for every adult; several correlative results and indirect evidence suggest that only high quality adults adopt. In conclusion, this study uncovered an interesting complexity underlying an apparently erroneous behavior in the parental care system of avocets. The findings contribute to an understanding of the evolution of the different forms of parental care and throw light on the possible evolutionary mechanisms that led to the current diversity of reproductive strategies in birds.

Item Type: Thesis (PhD)
Subjects: Q Science / természettudomány > QH Natural history / természetrajz > QH301 Biology / biológia
Q Science / természettudomány > QL Zoology / állattan
Depositing User: Erika Bilicsi
Date Deposited: 23 Aug 2013 08:02
Last Modified: 23 Aug 2013 08:02

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