American Woodcock Ecology and Bird Conservation in Relation to Forest Management.

摘要

The extent of shrubland and young forest in the Northeast, USA, has declined rapidly since the mid-1900's. Accordingly, the abundance of wildlife that depends on young forest has also declined. For example, American woodcock (Scolopax minor), an upland shorebird species, require an appropriate spectrum and spatial configuration of young forest to thrive and their populations have declined significantly since at least 1968. Active forest management is required to conserve populations of American woodcock and other young forest wildlife, but the importance of young forest management to some aspects of the ecology of key wildlife are not fully understood. I investigated three aspects of American woodcock ecology in relation to young forest management in Rhode Island, USA. First, I monitored the daytime locations of radio-marked American woodcock to assess habitat selection at multiple scales in relation to young forest management. Second, I also monitored American woodcock movements between daytime and nighttime locations and quantified food availability and predator activity at these sites to test the foraging-benefit and predation-risk hypotheses that were proposed to explain American woodcock commuting behavior. Third, I compared landbird communities at managed forest openings used by breeding American woodcock and nearby random forest sites to determine whether American woodcock habitat management benefits non-target landbirds and so verifies adopting American woodcock as an umbrella species useful for conservation.;Daytime habitat selected by American woodcock comprised areas of younger forest where the biomass of preferred food (i.e., earthworms [Haplotaxida]) was 1.7 -- 3.1 times greater, and the density of shrub and sapling stems was two times greater, compared to random sites. American woodcock home ranges were typically <50 ha and encompassed wetland forests and deciduous or mixed upland forests on flatter slopes ≤1.5 km from streams, agricultural openings, upland young forests, and moist soils. Across Rhode Island, most forested land was in the low - moderate classes of relative probability of use, but young forest management in key areas effectively increased relative use. I illustrated how land managers can use resource selection functions to predict the response of American woodcock to young forest management and so maximize conservation benefits.;All of the American woodcock I monitored commuted between dense forest stands and forest openings during the day and night, respectively. I found no support for the foraging-benefit hypothesis because individuals moved from daytime locations where earthworms were 3 -- 4 times more abundant to nighttime locations where preferred food was scarce. Soil moisture content was greater at daytime than nighttime locations which may explain why earthworms were more prevalent at those sites. In contrast, I found support for the predation-risk hypothesis because individuals moved from daytime locations where mammalian predators were more active to nighttime locations where mammalian predators were less active. Thus, American woodcock commuted between daytime and nighttime locations to avoid predators and not to feed. Maintaining forest openings is an important part of American woodcock habitat management so that individuals can eat by day and stay safe by night.;I identified 38 - 51 bird species during 10-minute point counts at American woodcock singing grounds and random forest sites, and 62 - 73% of the more frequently occurring species were more common at American woodcock singing grounds. On average, 55% of the more common species at American woodcock singing grounds were of high regional or local conservation priority. Young forest species such as prairie warbler (Setophaga discolor) and gray catbird (Dumetella carolinensis) were more abundant at American woodcock singing grounds and scarce or absent at random forest sites while the opposite was true for more mature forest species such as ovenbird (Seiurus aurocapilla) and red-eyed vireo (Vireo olivaceus). Moreover, the total number of birds (all species combined) and diversity of birds were ≥1.5 times greater at American woodcock singing grounds than random forest sites. Critical breeding sites for American woodcock can be managed by clearcutting ≥2-ha patches of older secondary forest and many other young forest bird species of conservation priority inhabit these managed areas. Thus, the American woodcock can serve as an effective umbrella species for young forest birds in the Northeast, USA, but complementary umbrella species such as the ovenbird should be considered to aid in the conservation of more mature forest birds.