Co-occurrence and nest success of Thick-billed and Chestnut-collared Longspurs in a central Montana rangeland

Shea P. Coons, Kaitlyn M. Reintsma, Victoria J. Dreitz

Research output: Contribution to journalArticlepeer-review

Abstract

Thick-billed and Chestnut-collared Longspurs (Rhynchophanes mccownii and Calcarius ornatus, respectively) are 2 grassland bird species that are indicative of the widespread decline of grassland passerines in North America. In our central Montana study area, we observed these 2 species nesting within close proximity (< 40 m apart), suggesting that this study area may hold conservation value due to its capacity to support breeding individuals of both species. Given their declining populations and our limited knowledge of their nesting ecology, our objective was to examine the nest success and interspecies nest distances of Thick-billed and Chestnut-collared Longspurs in a central Montana rangeland. We conducted systematic and opportunistic nest searches from 2013 to 2019 to determine nest fate and nest locations. We found a total of 259 Thick-billed Longspur nests and 34 Chestnut-collared Longspur nests. Incubation survival rates were 0.45-0.61 for Thick-billed Longspurs and 0.50-0.81 for Chestnut-collared Longspurs. Nestling survival rates were generally higher than incubation rates, ranging from 0.39 to 0.88 for Thick-billed Longspurs and 0.72 to 0.90 for Chestnut-collared Longspurs. The estimated survival rate for incubation and nestling stages combined was 0.19-0.43 for Thick-billed Longspurs and 0.36-0.73 for Chestnut-collared Longspurs. Chestnut-collared Longspur nests were frequently found in the same pasture as Thick-billed Longspur nests, with a total of 28 Chestnut-collared Longspur nests sharing pastures with 62 Thick-billed Longspur nests. The mean distance between Chestnut-collared Longspur nests and the nearest Thick-billed Longspur nest was 370 m (SE = 95 m) and ranged from 32 to 2230 m. Our work provides additional insights into the nesting ecology of these declining grassland songbird species by identifying a region that can support successful reproduction for both Thick-billed and Chestnut-collared Longspurs.

Original languageEnglish
Pages (from-to)219-224
Number of pages6
JournalWestern North American Naturalist
Volume84
Issue number2
DOIs
StatePublished - Jul 10 2024

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