Brood care strategies in shorebirds – Lada MÍŠKOVÁ

Abstract:

Parental care is a key life-history strategy in animals that strongly influences offspring survival and overall reproductive success. Although many studies have investigated the diversity of bird breeding strategies, a comprehensive syntheses of this topic on a global scale remain rare. This thesis addresses this gap by focusing on brood care strategies in shorebirds, a group exhibiting a wide diversity of parental care. Using a dataset comprising 23 variables for 254 shorebird species, the study examines variation in egg, clutch, and annual investment, hatching mass, precociality, fledging time, parental presence, brood mobility, coloniality, parental aggressiveness, and breeding latitude, as well as associations among these traits and their potential links to chick survival and population trends. Reproductive investment averaged approximately 11% of female body mass per egg, 48% per clutch, and 63% per breeding season, but varied substantially among species. Hatching mass was generally low (around 15 g), while most species were highly precocial, with chicks being relatively independent soon after hatching. Fledging typically occured around 30 days. In most species, both parents contributed to chick rearing. Chicks usually remained near the nest site after hatching but generally tended to move progressively farther away with increasing age. Most species bred solitarily, with colonial breeding occurring only rarely. Similarly, parental aggressiveness was generally low, with passive defence strategies predominating. Several significant correlations were identified among brood care strategies. Negative relationships between reproductive investment and hatching mass indicate trade-offs between initial parental investment and offspring traits. Parental aggressiveness was negatively associated with reproductive investment and positively associated with longer fledging times, indicating that behavioural strategies co-vary with investment-related traits. Associations between fledging time and both hatching mass and investment-related variables indicate linked variation in developmental timing and reproductive allocation. However, weak or absent correlations among several brood care strategies suggest their relative independence across shorebirds. No significant relationships between brood care strategies and demographic parameters were detected after correction for multiple testing. However, chick survival showed a trend for negative association with higher precociality and parental aggressiveness, while population trends were positively associated with lower brood mobility and longer fledging time. Future research should aim to define still unknown brood care strategies for multiple shorebird species. Overall, brood care strategies in shorebirds reflect species-specific life histories and environmental conditions, providing a basis for future research on their adaptive significance in a changing world. …víceméně

Abstract:

Parental care is a key life-history strategy in animals that strongly influences offspring survival and overall reproductive success. Although many studies have investigated the diversity of bird breeding strategies, a comprehensive syntheses of this topic on a global scale remain rare. This thesis addresses this gap by focusing on brood care strategies in shorebirds, a group exhibiting a wide diversity of parental care. Using a dataset comprising 23 variables for 254 shorebird species, the study examines variation in egg, clutch, and annual investment, hatching mass, precociality, fledging time, parental presence, brood mobility, coloniality, parental aggressiveness, and breeding latitude, as well as associations among these traits and their potential links to chick survival and population trends. Reproductive investment averaged approximately 11% of female body mass per egg, 48% per clutch, and 63% per breeding season, but varied substantially among species. Hatching mass was generally low (around 15 g), while most species were highly precocial, with chicks being relatively independent soon after hatching. Fledging typically occured around 30 days. In most species, both parents contributed to chick rearing. Chicks usually remained near the nest site after hatching but generally tended to move progressively farther away with increasing age. Most species bred solitarily, with colonial breeding occurring only rarely. Similarly, parental aggressiveness was generally low, with passive defence strategies predominating. Several significant correlations were identified among brood care strategies. Negative relationships between reproductive investment and hatching mass indicate trade-offs between initial parental investment and offspring traits. Parental aggressiveness was negatively associated with reproductive investment and positively associated with longer fledging times, indicating that behavioural strategies co-vary with investment-related traits. Associations between fledging time and both hatching mass and investment-related variables indicate linked variation in developmental timing and reproductive allocation. However, weak or absent correlations among several brood care strategies suggest their relative independence across shorebirds. No significant relationships between brood care strategies and demographic parameters were detected after correction for multiple testing. However, chick survival showed a trend for negative association with higher precociality and parental aggressiveness, while population trends were positively associated with lower brood mobility and longer fledging time. Future research should aim to define still unknown brood care strategies for multiple shorebird species. Overall, brood care strategies in shorebirds reflect species-specific life histories and environmental conditions, providing a basis for future research on their adaptive significance in a changing world. …víceméně