نتایج جستجو برای: wintering
تعداد نتایج: 2246 فیلتر نتایج به سال:
Identifying post-breeding migration and wintering distributions of migratory birds is important for understanding factors that may drive population dynamics. Red-throated Loons (Gavia stellata) are widely distributed across Alaska and currently have varying population trends, including some populations with recent periods of decline. To investigate population differentiation and the location of...
The overall distribution of wintering sandhill cranes in Mexico has been reported and summarized in several prior documents. However, most reports are associated with counts or surveys primarily conducted for wintering waterfowl. Recent (19992002) reports compiled from local researchers show, that wintering sandhill cranes are distributed much more widely in northern Mexico than is currently re...
Winter is a very important period during the dairying calendar. Regions such as Southland, with susceptible soils and extended periods with soils at saturation levels will face increasing pressure to review wintering practices. On-farm options for wintering cows to protect soils and prevent pasture damage are needed. This requires a turn-around in philosophy from taking cows to pasture/crops, t...
Scientists and birdwatchers alike have noted precipitous population declines in many species of migratory songbirds during the last thirty years. However, the transitory nature of migratory birds makes it difficult to pinpoint the exact cause of these declines. Some postulate that habitat loss on the tropical wintering grounds is the cause, while others suggest that forest degradation on the te...
Long-distance migration in birds is relatively well studied in nature; however, one aspect of this phenomenon that remains poorly understood is the pattern of distribution presented by species during arrival to and establishment of wintering areas. Some studies suggest that the selection of areas in winter is somehow determined by climate, given its influence on both the distribution of bird sp...
A primary constraint on effective conservation of migratory animals is our inability to track individuals through their annual cycle. One such animal is the endangered southwestern subspecies of the Willow Flycatcher, which is difficult to distinguish from conspecifics. Identifying wintering regions used by the endangered subspecies would be an important step in formulating an effective conserv...
Climate change is predicted to cause changes in species distributions and several studies report margin range shifts in some species. However, the reported changes rarely concern a species' entire distribution and are not always linked to climate change. Here, we demonstrate strong north-eastwards shifts in the centres of gravity of the entire wintering range of three common waterbird species a...
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