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Adopting Behavior and Breeding Biology of Avocets: Benefits of Large Broods for Good Parents?
Get PDFAlloparental 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
Effect of a Cyanobacterial Biomass enriched with Trace Elements on Thermophilic Dairy Starter Cultures
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