Detecting ecological traps inhuman‐alteredlandscapes: A case study of the thick‐billed longspur nesting in croplands

Abstract

Conversion of the North American prairies to cropland remains a prominent threat to grassland bird populations. Yet, a few species nest in these vastly modified systems.Thick-billed longspurs historically nested in recently disturbed or sparsely vegetated patches within native mixed-grass prairie, but observations of longspurs in spring cereal and pulse crop fields during the breeding season in northeastern Montana, USA, suggest such fields also provide cues for habitat selection. Maladaptive selection for poor-quality habitat may contribute to ongoing declines in longspur populations, but information on thick-billed longspur breeding ecology in crop fields is lacking. We hypothesized that crop fields may function as ecological traps; specifically, we expected that crop fields may provide cues for territory selection, but frequent human disturbance would result in reduced reproduction. To address this hypothesis, we compared measures of habitat selection (settlement patterns and trends in abundance) and productivity (nest density, nest survival, and number of young fledged) between crop fields and native grassland sites during 2020-2021. Across both years, settlement patterns were similar between site types and occupancy ranged from 0.52 ± 0.17 SE to 0.99 ± 0.01 on April 7 and 30, respectively. Early season abundance differed by year, and changes in abundance during the breeding season appeared to be associated with precipitation-driven vegetation conditions rather than habitat type. While an index of nest density was lower in crop than native sites, the number of young fledged per successful nest (2.9 ± 0.18 SE) and nest survival (0.24 ± 0.03 SE; n = 222 nests) were similar for crop and native sites. Collectively, the data did not support our ecological trap hypothesis: longspurs did not exhibit a clear preference for crop sites and reproductive output was not significantly reduced. Our results indicate that croplands may provide alternative breeding habitat within a human-dominated landscape.

Springtime bird use of agricultural landscapes examined by using autonomous recording units

“…Buxton et al (2016) used ARUs to examine shifts in arrival of migratory songbirds in Alaska and found bioacoustic indices to be useful for tracking arrival of songbirds. Swicegood et al (2023) deployed ARUs in agricultural landscapes to investigate settlement patterns of Thick-billed Longspurs (Rhynchophanes mccownii). Other springtime studies include Sanders and Mennill (2014) and Colbert et al (2015), which used ARUs to examine spring migratory movements and spring gobbling activity of Wild Turkey (Meleagris gallopavo), respectively.…”