Range-Wide Patterns of Natal and Breeding Dispersal in the Streaked Horned Lark

Abstract

The streaked horned lark (Eremophila alpestris strigata) is a federally-threatened ground-nesting passerine. We investigated range-wide patterns of dispersal by analyzing resight records between 2002 and 2016 from four regions (South Puget Lowlands, Lower Columbia River, Washington Coast, Willamette Valley) and determined frequency and distances of dispersal events for second-year (SY, natal dispersal) and after second-year adults (ASY, breeding dispersal). Of 148 SY adults originally banded as dependent young and subsequently resighted as breeders, 111 (75%) returned to their natal breeding site and 37 (25%) dispersed to new sites. Among the latter, only two individuals dispersed to a different region. For natal dispersers that left their natal site, mean dispersal distance was 20.5 ± 26.8 km (± SD, median = 11.7 km) although most (73%) travelled less than 15 km. Female natal dispersers moved to new sites more frequently than males (29% versus 20%), which is consistent with typical female-biased dispersal in birds. In contrast to SY birds, ASY birds largely remained at the site where they spent their first potential breeding season (68 of 71; 96%). No adults left the region in which they first bred. These patterns of natal dispersal, emigration, and immigration can inform conservation planning by contributing to priorities for land protection.