Effect of Age on the Foraging Behaviour of Grey Heron Ardea Cinerea L., 1758 at a Submontane Dam Reservoir in the Post-Breeding Season

Abstract

The components of foraging behaviour and success of adult and juvenile Grey Heron Ardea cinerea were studied at the Dobczyce Reservoir (southern Poland) in July and September 2015. Juvenile and adult birds moved at similar rates during both months. Fish capture attempt rate was significantly higher for juvenile birds than for adults in July but not in September. Capture rate and foraging success probability (number of captures over all attempts) was significantly lower in juveniles in July but not in September. The foraging success probability of juveniles increased from July to September. Adult and juvenile birds caught mostly small fish, with no differences in size. However, handling time in juvenile birds was much longer than in adults in July but not in September, after controlling for differences in prey size. Thus, juvenile Grey Heron increased their efficiency of catching fish from July to September by reducing the number of mistakes, probably as a result of experience.

Comparação Da Eficiência De Forrageio Das Garças Egretta Caerulea E Egretta Thula No Estuário De Paranaguá, Paraná, Sul Do Brasil

“…Os jovens ingerem alimento suficiente para sua sobrevivência, mesmo gastando mais energia e consumindo menos, e com o tempo suas exigências nutricionais aumentam junto com a melhora de suas habilidades de forrageio. Portanto, a idade e o período de aprendizagem por experiência, associado à melhora das condições físicas dos jovens, podem ser fatores importantes no aumento da eficiência de forrageio da espécie, como demonstrado para outras espécies de garça (Gwiazda et al 2017).…”