Abstract
An animal's choice of foraging habitat reflects its response to environmental cues and is likely to vary among individuals in a population. Analyzing the magnitude of individual habitat selection can indicate how resilient populations may be to anthropogenic habitat change, where individually varying, broadly generalist populations have the potential to adjust their behavior. We collected GPS point data from 39 European nightjars (Caprimulgus europaeus) at a UK breeding site where restoration measures have altered large areas of habitat between breeding seasons. We calculated individual habitat selection over four breeding seasons to observe changes that might align with change in habitat. We also analyzed change in home range size in line with change in habitat availability, to examine functional relationships that can represent trade‐offs made by the birds related to performance of the habitat.Individual explained more of the variation in population habitat selection than year for most habitat types. Individuals differed in the magnitude of their selection for different habitat types, which created a generalist population composed of both generalist and specialist individuals. Selection also changed over time but only significantly for scrub habitat (60% decrease in selection over 4 years). Across the population, individual home range size was 2% smaller where availability of cleared habitat within the home range was greater, but size increased by 2% where the amount of open water was higher, indicating the presence of trade‐offs related to habitat availability. These results highlight that using individual resource selection and specialization measures, in conjunction with functional responses to change, can lead to better understanding of the needs of a population. Pooling specialist and generalist individuals for analysis could hide divergent responses to change and consequently obscure information that could be important in developing effective conservation strategies.
Highlights
An animal's decision-making process should drive it to use habitat that improves its chances of survival and reproductive success (Dussault et al, 2005; Leclerc, 2016; Owen, Swaisgood, & Blumstein, 2017; Roever, Beyer, Chase, & van Aarde, 2014), often making decisions based on one or more environmental cues, such as habitat type or structure
Individual home range size was 2% smaller where availability of cleared habitat within the home range was greater, but size increased by 2% where the amount of open water was higher, indicating the presence of trade-offs related to habitat availability
Functional responses refer to a change in movement behavior or habitat use in response to a change in habitat availability and may represent ecological trade-offs related to habitat type (Mabille, Dussault, Ouellet, & Laurian, 2012), conspecific interaction and competition (Buskirk & Millspaugh, 2006; Jones, 2001; Lesmerises, Déry, Johnson, & StLaurent, 2018), avoidance of predators (Mao et al, 2005), or human influence (Karelus, McCown, Scheick, van de Kerk, & Oli, 2016; Sawyer, Nielson, Lindzey, & McDonald, 2006)
Summary
An animal's decision-making process should drive it to use habitat that improves its chances of survival and reproductive success (Dussault et al, 2005; Leclerc, 2016; Owen, Swaisgood, & Blumstein, 2017; Roever, Beyer, Chase, & van Aarde, 2014), often making decisions based on one or more environmental cues, such as habitat type or structure. As the nightjar is a relatively range-limited species, detailed information on individual habitat selection and foraging movements is needed to measure behavioral, and potentially functional, responses to planned habitat change. We quantified nightjar home range and habitat selection behavior over the four-year period of landscape change, by analyzing GPS point data, which provided us with useful land management information on a suitable scale. We hypothesized that home range size would increase over the course of the restoration works and that the mechanism behind both an increase in home range size and habitat selection strength, as mentioned above, would relate to the decrease in invertebrate-rich foraging resources within nightjar territories This would cause the birds to forage over a wider area, due to areas having been cleared, but to be more selective within this area, because key foraging resources have been removed or divided. We hypothesized that increased wetland habitat types would push nightjars to forage over wider areas
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