| Steven A Munoz; Institute for Wildlife Studies; munoz@iws.org; Susan, Meiman, Emma, DeLeon, Melissa, A, Booker, Andrew, S, Bridges |
| The San Clemente Bell's sparrow (Artemisiospiza belli clementeae), a federally threatened sub-species, was thought to nest almost exclusively in California boxthorn (Lycium californicum) habitat, which was thought to limit long-term population viability. Recent monitoring efforts documented Bell's sparrows nesting in new habitats. We investigated whether nest sites have similar vegetative structure and shrub cover in boxthorn habitat as in newly occupied habitats. From 2014-2016, we sampled 215 Bell's sparrow nests and supporting habitats. We measured shrub cover and vegetation height in a 15m radius around each nest and nest substrate height. We found shrub cover was significantly (F2, 39.5 =16.6, P<0.001) greater surrounding nests located in sagebrush (Artemisa sp.; mean=38.1, n=29) and boxthorn (mean=44.9, n=166) habitats than non-boxthorn/non-sagebrush (mean=25.5, n=20) habitats. Average height of vegetation also differed (F2, 33.5=42.0, P<0.001) among habitat categories and was highest in sagebrush (mean= 28.3cm, n=29) and lowest in boxthorn (mean=16.8cm, n=166). Nest shrubs were significantly (F2, 35.2=22.8, P<0.001) shorter in boxthorn (mean=49.8cm, n=166) and non-boxthorn/non-sagebrush (mean=53.6cm, n=20) habitats than in sagebrush (mean=80.9cm, n=29). Our findings reveal Bell's sparrows select more diverse nest micro-habitats than previously thought, which may reduce vulnerability of Bell's sparrow population to stochastic events and improve prospects for this sub-species' recovery.
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