We examined key factors thought to influence Mourning Dove (Zenaida macroura) nest density (nests/ha) in Blue Oak woodlands (Quercus douglasii), riparian woodlands (Salix spp., Populus fremontii), and commercial walnut (Juglans spp.) orchards in northern California (north of UTM: Zone 51N, 324397E, 4207703N, datum WGS84). We hypothesized that nest density could be used to characterize the suitability of habitats for breeding Mourning Doves because nest success has often been shown to not vary predictably by habitat type. Because weather does affect nest success, we examined the influence of spring rainfall and ambient temperature, as well as habitat on nest density. We recorded all Mourning Dove nests found in surveys conducted every 3rd wk from mid-April to mid-August, which encompassed the nesting season, in each of 6 to 10 randomly placed survey plots in each of 4 study areas during 1992–1995, with a supplemental survey during September 1994. Survey date, habitat type, and spring weather affected period nest density (PND; mean number of all active nests/ha present during any given survey); and habitat type and weather affected cumulative nest density (CND; total number of different nests produced annually/ha). Seasonally, PND was relatively low in April, high from May to July, lower in August, and zero by September. Riparian woodlands tended to support higher PND and CND compared to walnut orchards and Blue Oak woodlands in that order. This effect was pronounced during the warm-dry springs of 1992 and 1994, but was not always evident during the relatively cool-wet springs of 1993 and 1995 (weather characterized relative to April mean high temperature and March to May mean rainfall). The best predictive model (lowest AICC) for PND contained a quadratic trend with survey timing, and effects due to habitat type, high temperature and rainfall deviations from long-term average, number of rain-days, and tree density. The best model for CND contained habitat, temperature, rainfall, rain-days, and tree density. Nest success increased at a declining rate as nest density increased in Blue Oak and riparian woodlands, demonstrating probable density-dependent resource or mortality limits on nest success that did not affect nest density within the ranges we recorded. Nest density measures should be useful to land managers in assessing responses of nesting Mourning Doves to available nesting habitats and local spring weather.
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Vol. 91 • No. 2