The Shelduck (Tadorna tadorna) is a characteristic waterbird species of inland wetlands in northeastern Algeria. Its wintering behavior in relation to changes of local abundances and foraging group density is poorly known. This study aims at monitoring patterns of diurnal activities and the variation of behavioral time-budgets in relation to numbers of wintering Shelducks. We investigate temporal variations of diurnal activities across multiple-time scales and consider their interrelationships. Assessments of local population abundance were weekly surveyed during two wintering seasons (2010–2012), whereas diurnal activities (feeding, sleeping, swimming, preening, loafing, flying, courtship, and antagonism) were studied three times a month during seven hours (08:00–16:00) using the Scan method. Time budget variations of each behavioral activity were tested using nested ANOVAs following multiple time scales. Generalized linear mixed-effects models (GLMM) tested whether variations in diurnal activities were density-dependent. During the wintering season, Shelduck’s numbers followed a bell-shaped trend, which indicated that the species was typically a wintering migrant in Sabkha Djendli. The first individuals arrived onsite in October–November then numbers reached a peak in January (up to 2400 individuals in 2012) with steady density during December–February, afterward individuals left the site progressively until late April when the site is deserted. During both wintering seasons, diurnal activities were dominated by feeding (60%), followed by sleeping (12%) then swimming and preening with 9% and 8%, respectively. The rest of the activities (loafing, flying, courtship and antagonistic behaviors) had low proportions of time budget. ANOVAs showed that activity time budgets varied significantly following multiple time scales (year, season, month, day, semi-hour). Time budgets of diurnal activities during each wintering season were significantly interrelated. Correlations patterns between the two seasons were similar. GLMMs revealed that the variations of diurnal activities were not density-dependent, except for preening and swimming. During the wintering season, habitats of Sabkha Djendli are important for waterbirds, including the Shelduck that used the lake mainly for food-foraging and resting. The 2400 individuals censused in mid-winter are important locally and at the North African scale. This stresses the need to strengthen the protection status of this wetland and mitigate degradation sources that threaten wintering waterfowl.

中文翻译：

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阿尔及利亚的谢尔达克（Tadorna tadorna）越冬的昼夜时间预算和活动方式是否与密度相关？跨多个时间尺度的分析

Shelduck（Tadorna tadorna）是阿尔及利亚东北部内陆湿地的一种典型水鸟物种。与局部丰度变化和觅食种群密度有关的越冬行为鲜为人知。这项研究的目的是监测昼夜活动的模式以及行为时间预算的变化与谢尔德越冬的数量有关。我们调查了跨多个时间尺度的昼间活动的时间变化，并考虑了它们之间的相互关系。在两个冬季（2010-2012）期间每周进行一次当地人口丰富度评估，而在七个小时内，每月进行三次昼夜活动（进食，睡觉，游泳，梳妆，游荡，飞行，求偶和拮抗）（08） ：00–16：00）。使用嵌套的方差分析按照多个时间尺度对每个行为活动的时间预算变化进行了测试。广义线性混合效应模型（GLMM）测试了昼间活动的变化是否与密度有关。在越冬季节，Shelduck的数量呈钟形趋势，这表明该物种通常是Sabkha Djendli的越冬移民。第一批人员在10月至11月到达现场，然后在1月至2月达到峰值（2012年达到2400人），并在12月至2月保持稳定的密度，随后个体逐渐离开现场，直到4月下旬该场地荒废为止。在两个冬季，昼夜活动主要由进食（60％），其次是睡觉（12％），然后游泳和节食（分别为9％和8％）决定。其余的活动（闲逛，飞行，求偶和敌对行为）的时间预算所占比例很小。方差分析显示，活动时间预算在多个时间尺度（年，季节，月，日，半小时）之后发生显着变化。每个冬季的昼间活动时间预算相互关联。两个季节之间的相关模式相似。GLMMs揭示了昼夜活动的变化与密度无关，除了梳理和游泳。在越冬季节，Sabkha Djendli的栖息地对水鸟很重要，其中包括Shelduck，该湖主要将湖用于觅食和休息。在冬季中期进行的2400例人口普查在当地和北非地区都很重要。