@article {KNZ002009, title = {Social interactions do not drive territory aggregation in a grassland songbird}, journal = {Ecology}, volume = {101}, year = {2020}, pages = {e02927}, abstract = {

Understanding the drivers of animal distributions is a fundamental goal of ecology and informs habitat management. The costs and benefits of colonial aggregations in animals are well established, but the factors leading to aggregation in territorial animals remain unclear. Territorial animals might aggregate to facilitate social behavior such as (1) group defense from predators and/or parasites, (2) cooperative care of offspring, (3) extra-pair mating, and/or (4) mitigating costs of extra-pair mating through kin selection. Using experimental and observational methods, we tested predictions of all four hypotheses in a tallgrass prairie in NE Kansas, USA. Grasshopper Sparrow (Ammodramus savannarum) males formed clumps of territories in some parts of the site while leaving other apparently suitable areas unoccupied. Despite substantial sampling effort (653 territories and 223 nests), we found no support for any hypothesized social driver of aggregation, nor evidence that aggregation increases nest success. Our results run counter to previous evidence that conspecific interactions shape territory distributions. These results suggest one of the following alternatives: (1) the benefits of aggregation accrue to different life history stages, or (2) the benefits of territory aggregation may be too small to detect in short-term studies and/or the consequences of aggregation are sufficiently temporally and spatially variable that they do not always appear to be locally adaptive, perhaps exacerbated by changing landscape contexts and declining population sizes.

}, keywords = {LTER-KNZ}, doi = {10.1002/ecy.2927}, url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/ecy.2927}, author = {Winnicki, S.K. and Mungu{\'\i}a, S.M. and Williams, E.J. and W. A. Boyle} } @article {KNZ001889, title = {Causes and consequences of avian within-season dispersal decisions in a dynamic grassland environment}, journal = {Animal Behaviour}, volume = {155}, year = {2019}, pages = {77 - 87}, abstract = {

Understanding the causes and consequences of dispersal is key to identifying selective pressures underlying species-level variation in biogeography, metapopulation dynamics and adaptive capacity. We tested the hypotheses that nest predation and/or brood parasitism avoidance drive breeding dispersal decisions and that dispersal functions to reduce subsequent reproductive failure in grasshopper sparrows, Ammodramus savannarum, breeding in eastern Kansas, U.S.A. Over 2 years, we monitored the fate of 222 nests and the movements of 144 parents. We established the spatiotemporal patterns of nest success among all nests, then related nest predation and parasitism to subsequent dispersal behaviour and reproductive success. Birds were more likely to disperse following nest predation, but decisions were unaffected by parasitism. Dispersers experienced higher chances of subsequent nest survival than did site-faithful individuals. Although second nests were parasitized less often than were first nests, dispersers did not experience substantially lower parasitism than did site-faithful individuals, suggesting that the challenges of predation and brood parasitism may be solved in different ways. This study represents one of few tests of alternative hypotheses explaining dispersal decisions of songbirds within seasons and represents a rare case study of the consequences of breeding dispersal on subsequent reproductive success. Our results suggest that differences in dispersal tendencies may result from variation in risk-response thresholds rather than alternative causal drivers.

}, keywords = {LTER-KNZ, breeding dispersal, habitat variability, nomadism, settlement, territory switching, within-season dispersal}, doi = {10.1016/j.anbehav.2019.06.009}, url = {https://doi.org/10.1016/j.anbehav.2019.06.009}, author = {Williams, E.J. and W. A. Boyle} } @article {KNZ001817, title = {Patterns and correlates of within-season breeding dispersal: a common strategy in a declining grassland songbird}, journal = {The Auk: Ornithological Advances}, volume = {135}, year = {2018}, pages = {1-14}, abstract = {

Dispersal is a ubiquitous behavior with important consequences for gene flow, demography, and conservation. Some birds engage in between-year breeding dispersal, but the factors shaping variation in this behavior are not well understood. In mid-continental grasslands, preliminary evidence suggested that Grasshopper Sparrows (Ammodramus savannarum) dispersed not only between seasons, but also within breeding seasons\—an apparently uncommon avian behavior. We studied a population of Grasshopper Sparrows breeding in northeastern Kansas, USA, to document the spatial and temporal patterns of within-season breeding dispersal in an experimentally managed tallgrass prairie from 2013 to 2015. We combined color-band resighting, territory mapping, and radio telemetry to quantify changes in territory density, turnover of territorial males, and dispersal distances. Density of Grasshopper Sparrows varied seasonally in management-specific ways, simultaneously increasing and decreasing in watersheds that differed in management regime. Turnover was unexpectedly high, with over half of territorial males being replaced each month. We documented over a third of males dispersing up to \∼9 km between breeding attempts. Our study provides the first comprehensive description of the patterns of within-season breeding dispersal in a grassland songbird. Our results reveal the remarkable prevalence of within-season movement in this system and the relatively large distances over which birds disperse. Such mobility has important implications for survey design and habitat management, as birds select habitat at much larger spatial scales than is generally appreciated. These results also provide foundational information for tests of alternative hypotheses explaining the ecological and evolutionary basis for such movements.

}, keywords = {LTER-KNZ, Grasslands, inter-patch movement, intra-season movement, Konza Prairie, LTER, mid-season habitat shifts, territory switching}, doi = {10.1642/AUK-17-69.1}, url = {http://www.bioone.org/doi/pdf/10.1642/AUK-17-69.1}, author = {Williams, E.J. and W. A. Boyle} } @mastersthesis {KNZ001734, title = {Grasshopper sparrows on the move: patterns and causes of within-season breeding dispersal in a declining grassland songbird}, volume = {MS Thesis}, year = {2016}, school = {Kansas State University}, type = {M.S. Thesis}, address = {Manhattan, KS}, keywords = {LTER-KNZ}, url = {http://krex.k-state.edu/dspace/handle/2097/32705}, author = {Williams, E.J.} }