nestling growth in common kestrels

Nestling growth is an important trait in the life-history strategy of avians and influences later survival and reproductive success. In addition to the determination of individual fitness, growth rates might also be sensitive indicators of ecological conditions and environmental changes. This is particularly important in the case of birds, which are the top predators in the food chain. In this study, we examined the combined effects of habitat characteristics and biological factors on the nestling growth of the common kestrel (Falco tinnunculus). Daily changes in four biometric traits, expressed as percentages of their baseline values, were used to determine relative growth rates. Brood size, hatching order, and breeding phenology significantly influenced the growth rates of Kestrel nestlings. Nestlings in broods four presented the lowest growth increases, whereas those in larger broods presented greater values. Among the largest broods, the fifth and sixth nestlings grew faster than their younger siblings did. Relative growth rates were also positively correlated with the date of the first egg. In contrast, habitat characteristics had no measurable effect on growth rates. Our findings highlight the relevance of nestling growth parameters as indicators of breeding performance and may support the effectiveness of kestrel conservation programs in rural landscapes. We recommend incorporating chick growth rates as a valuable biological parameter in the evaluation of raptor conservation efforts.