Parental resource allocation among offspring varies with increasing brood age in Black-legged Kittiwakes Rissa tridactyla

Abstract

Capsule Black-legged Kittiwakes Rissa tridactyla breeding at a North Sea colony allocated more resources to younger chicks with increasing brood age.Aims Examine how feeding, attendance and resource allocation change with increasing brood age and how allocation of feeds affects growth rate and fledging success.Methods Broods of two were observed on Coquet Island to compare feeding rates and fledging success between chicks of different hatching order.Results Growth and feeding rates were similar between chicks of different hatching order. The relationship between growth and feeding rate may have differed between siblings, although this relationship was not strong. Feeding rate per brood and nest attendance decreased nonlinearly as brood age increased. First-hatched chicks were fed more frequently at the beginning of multiple feeds and received a higher proportion of feeds during early chick-rearing. However, during late chick-rearing second-hatched chicks received proportionally more feeds.Conclusion Parents reduced overall feeding rate as brood age increased, while increasing the proportion of resources allocated to younger offspring. This may explain general similarities in growth rate and fledging success between chicks of different hatching order. By considering resource allocation throughout development we can better understand parental investment strategies in asynchronous species.