Lead Shot in Some Spring Migrant Ducks

The incidence of lead shot in l ,687 lesser scaup (Athya affinis) and 416 ring-necked ducks (Athya collaris) in spring migration in Minnesota and the implications as related to the bird population and hunting harvest the preceding fall are considered in this study. The ducks, which were examined for shot by photofluorographic radiography had died as a result of oil pollution on the Mississippi River in the vicinity of Red Wing in the spring of 1963. The birds were separated into two age groups and by sex. Yearling lesser scaup had a body shat incidence (proportion of birds containing shot) of 5.5 per cent and yearling ring-necked ducks 17.8 per cent. For both species, yearling males had a higher incidence of shot than yearling females, and the most common location of shot was just beneath the skin on the back and abdomen. By using shot incidence in conjunction with other data, the harvest rate during the preceding hunting season (1962) was estimated as being 15 to 20 per cent of the population for yearling lesser scaup of both sexes; 30 to 35 per cent far yearling female ring-necked ducks, 60 to 70 per cent for yearling males, and 45 to 55 per cent for yearlings of both sexes of ring-necked ducks combined. Incidence of ingested shot in the digestive tracts of the birds (mostly gizzard) was low, being 1.7 per cent for lesser scaup and 1.6 per cent far ring-necked ducks

Decadal changes and delayed avian species losses due to deforestation in the northern Neotropics

How avifauna respond to the long-term loss and fragmentation of tropical forests is a critical issue in biodiversity management. We use data from over 30 years to gain insights into such changes in the northernmost Neotropical rainforest in the Sierra de Los Tuxtlas of southern Veracruz, Mexico. This region has been extensively deforested over the past half-century. The Estación de Biología Tropical Los Tuxtlas, of the Universidad Nacional Autónoma de México (UNAM), protects a 640 ha tract of lowland forest. It became relatively isolated from other forested tracts between 1975 and 1985, but it retains a corridor of forest to more extensive forests at higher elevations on Volcán San Martín. Most deforestation in this area occurred during the 1970s and early 1980s. Forest birds were sampled on the station and surrounding areas using mist nets during eight non-breeding seasons from 1973 to 2004 (though in some seasons netting extended into the local breeding season for some species). Our data suggested extirpations or declines in 12 species of birds subject to capture in mist nets. Six of the eight species no longer present were captured in 1992–95, but not in 2003–2004. Presence/absence data from netting and observational data suggested that another four low-density species also disappeared since sampling began. This indicates a substantial time lag between the loss of habitat and the apparent extirpation of these species. Delayed species loss and the heterogeneous nature of the species affected will be important factors in tropical forest management and conservation

Avian distribution and abundance records for the Sierra de Los Tuxtlas

ABSTRACT.-Between 1973 and 1987 we spent more than 36 months studying birds in the Sierra de Los Tuxtlas, on the Gulf coast of southern Veracruz, Mexico. This area contains the northernmost tropical rainforest in the western hemisphere, and has undergone relatively rapid deforestation in the past three decades. Its avifauna is diverse, consisting of both resident and migratory birds. We recorded 405 species, including 58 that have not been reported from the region before, as well as several that apparently have not been reported for Veracruz. Fully 350 species are documented by specimens; the remaining 55 consist of sight records only. We compare our results with past surveys of Los Tuxtlas and discuss 124 species whose status in the region is affected by our data. Of the 405 species we recorded in Los Tuxtlas, 96 (23.7%) appear on a list of bird species from the northern neotropics thought to be in danger due to tropical deforestation. Received 9 Jan. 1992, accepted 29 April 1992. The Sierra de Los Tuxtlas (hence Los Tuxtlas) is a rugged, mountainous region of volcanic origin, isolated from the Sierr