Free‐living birds need to acquire enough food to fulfil their energetic needs, which may require more effort in habitats with less favourable conditions. Therefore, to maintain their necessary energy intake, birds need to adjust their foraging behaviour in response to varying habitat conditions. In this study, we investigated the relationship between intake rates of free‐living Black‐tailed Godwits Limosa limosa limosa and their foraging behaviour, at various agricultural grasslands with different prey densities and habitat conditions. Based on video recordings obtained in the period between arrival to their breeding grounds and egg‐laying, we measured intake rates, probe, peck and step rates (i.e. foraging effort) and the peck/probe ratio (i.e. foraging mode) of individual birds feeding on soil fauna at self‐selected grasslands. Additionally, at the corresponding feeding sites, we assessed the soil prey density, soil moisture content and vegetation height. We did not find a relationship between intake rates and local prey densities or habitat conditions, nor did intake rates significantly change with increased foraging effort and shifts in foraging mode. These findings suggest that Black‐tailed Godwits adjusted their foraging behaviour to maintain constant intake rates. In moist soils, Black‐tailed Godwits showed a significantly lower probing and pecking effort when prey density was high. This indicates that soil moisture is an important mediator that improves habitat quality, possibly by affecting the ease of probing and/or the detection of subterranean prey through their vibratory cues. This study provides insights into the behavioural mechanisms through which Black‐tailed Godwits cope with habitat variation or degradation.
Veenstra et al. (Wed,) studied this question.