Distribuição espacial e temporal de aves limícolas (Charadriiformes) na Ilha dos Caranguejos, Golfão Maranhense, Brasil

Abstract

We studied spatial and seasonal distribution of shorebirds (Charadriiformes) in Island of Caranguejos, Gulf of Maranhão. Censuses were conducted seasonally (considering arrival of migrants in South America, wintering, departure and breeding in North America) from September/2007 to July/2008, in two sectors of Island, North and South. We used the methods of point count, transect and estimate. The North Sector showed greater richness, the South, most abundance. The North Sector did not show differences in number of individuals or significantly different (Kruskal-Wallis, H = 1.0163, df = 3, P = 0.7973) between the periods. The Southern Sector showed greater abundance in the arrival (35,046) winter (35,708), decline in departure (20,046) and increasing of abundance in reproductive period (92), showed no significantly different (Kruskal-Wallis , H = 4.1596, df = 3, P = 0.2447). Considering the total number of shorebirds, the following pattern was observed: high abundance during the period of arrival (46,698), and winter (41,263), followed by declines in the individuals numbers in departure (24,169) and reproductive (6071), not significantly different (Kruskal-Wallis, H = 28,892, df = 3, P = 0.4090). There was no significantly different considering the abundance of time of arrival (Mann-Whitney U = 44.00; Z = 0.7107, P = 0.4773), winter (Mann-Whitney U = 48.50; Z = 0.3909 P = 0.6959), departure (Mann-Whitney U = 38.00; Z = 11,371, P = 0.2555) and reproductive (Mann-Whitney U = 45.00; Z = 0.6396, P = 0 , 5224) between North and South. Temporal distribution showed a high abundance in the months September to November (autumn migration) and from December to February (winter) reducing the number of individuals in the months of March to May and low values were recorded from June to August, when the birds are breeding in Arctic. Calidris pusilla was the most abundant species in all periods. Spatial distribution was related to the change of tide. Island of Caranguejos is a important wintering site for migratory shorebirds, its conservation is important for maintenance of birds group in wild life.