Behavioral aspects of waterbirds

Abstract Estuaries are used by waterbirds as foraging, resting and nesting sites, serving also as shelter for migratory birds. The dynamics of this avifauna in an aquatic environment may be associated with the differences of time of day, tide height, temperature, wind speed and use of the site by different species. This study had the objective of evaluating behavioral aspects of aquatic birds, relating the influence of environmental variables with their activities. Bird counts were performed at the mouth of two important rivers of the state of Santa Catarina, Brazil, during two-hour intervals throughout the day in monthly samplings between June (2015) and May (2016). A total of 44 species were recorded, ten of which were migratory. The most recorded behaviors were foraging and resting. The Kruskal-Wallis analysis indicated no significant difference in behavior between the sampling intervals. The Bray-Curtis similarity test resulted in three groups: 1) - species that foraged most of the time; 2) - species that rested most of the time; and 3) - same time in both activities. The Indicator Species Analysis showed that 17 species were associated with only one microhabitat and 15 species with more than one. The Canonical Correlation Analysis indicated that only tide height, temperature and rainfall variables were correlated with the behaviors performed and only the resting activity was positively correlated with all variables. This may be associated with thermoregulation and the ability of some species to stay in midlitoral at high tide. The results demonstrate that different waterbird species used the studied areas in different ways. Thus, the heterogeneity of microhabitats in an aquatic environment of extreme importance for the coexistence and maintenance of the diversity of waterbirds.

摘要：河口是水鸟的觅食、休憩与筑巢场所，同时也是候鸟的庇护栖息地。
该水生环境中的鸟类区系动态，可能与日周期、潮高、气温、风速以及不同物种对该区域的利用模式差异相关。
本研究旨在评估水鸟的行为特征，探究环境变量对其行为活动的影响。
研究于2015年6月至2016年5月期间开展月度采样，每日以两小时为间隔，在巴西圣卡塔琳娜州两条重要河流的河口处进行鸟类计数。
本次调查共记录到44个鸟类物种，其中10种为候鸟。
观测到的主要行为类型为觅食与休憩。
克鲁斯卡尔-沃利斯检验（Kruskal-Wallis）分析结果显示，不同采样时段间的鸟类行为无显著差异。
通过布莱柯蒂斯相似性检验（Bray-Curtis similarity test），可将受试物种划分为3个类群：1）以觅食为主要行为的物种；2）以休憩为主要行为的物种；3）两种行为耗时相近的物种。
指示物种分析（Indicator Species Analysis）结果显示，17个物种仅与1种微生境相关联，15个物种则与多种微生境相关。
典范相关分析（Canonical Correlation Analysis）结果表明，仅潮高、气温与降雨量这三类环境变量与受试鸟类的行为存在相关性，且仅休憩行为与全部三类变量呈正相关。
该现象可能与体温调节（thermoregulation）以及部分物种在涨潮时栖息于中潮带的能力有关。
本次研究结果表明，不同水鸟物种对研究区域的利用模式存在差异。
因此，水生环境中的微生境异质性对于水鸟物种的共存与多样性维持极其重要。