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<p>Artificial light at night (ALAN) is increasingly recognised as a driver of behavioural change in urban wildlife, yet systematic evidence of diel niche expansion in tropical avian species remains limited. We investigated nocturnal foraging of cattle egrets (<i>Bubulcus (= Ardea) ibis</i>), a typically diurnal generalist, within an illuminated settlement in Rivers State, Nigeria. Observations were conducted during the dry and wet seasons, quantifying egret abundance, activity timing, insect availability, and light type preference. Nocturnal activity occurred routinely between 19:00 and ~ 01:50&#xa0;h, with significantly higher mean abundances in the dry season, coinciding with greater insect numbers under artificial lights. The number of foraging egrets was markedly higher under incandescent bulbs than randomly observed outside/nearby of artificial lights, showing that egrets primarily forage under artificial lights at night, with most individuals roosting in trees and only ~ 7.6% actively foraging. Nocturnal activity, concentrated between 19:00 and 01:50&#xa0;h, was significantly higher in the dry season, coinciding with increased insect abundance. Negative binomial Generalized Linear Models indicated that season and insect abundance per bulb were the strongest predictors of egret numbers, while hour and light type had no significant effect on insect abundance. Incandescent bulbs were visited more often, likely influenced by their spatial placement. These findings represent the first systematic documentation of ALAN-facilitated nocturnal foraging in <i>B. ibis</i>, and highlight how urban lighting can create alternative foraging opportunities, potentially influencing trophic dynamics in rapidly urbanising tropical ecosystems.</p>

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Artificial light drives nocturnal foraging in cattle egrets (Bubulcus ibis) in urban-modified wetlands of Southern Nigeria

  • 期刊论文

  • 发表日期：

    2025年12月18日

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  • Nioking Amadi,
  • Alawa Grace Nyimale,
  • Luca Luiselli,
  • Fabio Petrozzi,
  • Julia E. Fa,
  • Wala Chimela,
  • Wekhe-Emenike Aruchi,
  • Amadi Patience Ndidi,
  • Harrison Obodo Chukwu

摘要

Artificial light at night (ALAN) is increasingly recognised as a driver of behavioural change in urban wildlife, yet systematic evidence of diel niche expansion in tropical avian species remains limited. We investigated nocturnal foraging of cattle egrets (Bubulcus (= Ardea) ibis), a typically diurnal generalist, within an illuminated settlement in Rivers State, Nigeria. Observations were conducted during the dry and wet seasons, quantifying egret abundance, activity timing, insect availability, and light type preference. Nocturnal activity occurred routinely between 19:00 and ~ 01:50 h, with significantly higher mean abundances in the dry season, coinciding with greater insect numbers under artificial lights. The number of foraging egrets was markedly higher under incandescent bulbs than randomly observed outside/nearby of artificial lights, showing that egrets primarily forage under artificial lights at night, with most individuals roosting in trees and only ~ 7.6% actively foraging. Nocturnal activity, concentrated between 19:00 and 01:50 h, was significantly higher in the dry season, coinciding with increased insect abundance. Negative binomial Generalized Linear Models indicated that season and insect abundance per bulb were the strongest predictors of egret numbers, while hour and light type had no significant effect on insect abundance. Incandescent bulbs were visited more often, likely influenced by their spatial placement. These findings represent the first systematic documentation of ALAN-facilitated nocturnal foraging in B. ibis, and highlight how urban lighting can create alternative foraging opportunities, potentially influencing trophic dynamics in rapidly urbanising tropical ecosystems.