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This paper reports the results of an attempt to determine whether botulinus toxin or some other factor was responsible for avian sickness on water bodies in Minnesota, North and South Dakota, and at Whitewater Lake, Boissevain, Manitoba, in the summer of 1953.
No abstract available.
Gizzards and wingbones from immature mallards ( Anas platyrhynchos ), pintails ( Anas acuta ), black ducks ( A. rubripes ), and Canada geese ( Branta canadensis ) were collected from 12 national and stat hunting are.as during the hunting season of 1974-75. The gizzards were examined for the occurrence of lead and steel shot and the wingbones were analyzed for lead residues. Incidence of lead shot in gizzards ranged from 1.3 percent in mallards from Monte Vista National Wildlife Refuge to 29 percent in pintails from Sauvie Island Wildlife Management Area. Lead in wingbones ranged from trace residues (<0.5 ppm) to 345 ppm. The incidence of steel shot in gizzards surpassed lead shot on some refuges that have had mandatory steel shot programs. There was a significant correlation between frequency of lead shot in gizzards and lead residues in wingbones.
Abstract has not been submitted
The nesting behavior of a concentration of nesting mallards ( Anas platyrhynchos ) and gadwalls ( A. strepera ) was studied on a 4.5-ha island in Miller Lake, North Dakota, in 1977. A single 0.59-ha clump of thick shrub contained 225 simultaneously active mallard nests on 10 May. During the peak nesting period, mallard nests were spaced an average of 2.7 m from conspecifics. Active nests of all species peaked at 327, spaced an average of 2.1 m apart. Nests were clustered in thick shrub with moderate numbers in open shrub and few in grassland. Nest placement was significantly related to the amount of vegetative screening although mammalian predators were absent on the island. Cover density appeared to be important to the nesting hens as vegetation screened nests from potential avian predators and from harassment by other conspecific nesting hens and drakes. Mallards and gadwalls nesting on this island used wetlands in >100 km2 around Miller Lake. During daylight hours in late April 1978, an average of 4.9 mallards/minute arrived at the island; a peak of 17.2 mallards/minute arrived at 0800. In late April 1978, as many as 26 mallard pairs/ha occurred on favored wetlands and behavioral aggression was intense. Yet, most mallard hens maintained adequate space to acquire food and other requisites. Mallards and gadwalls were sufficiently adaptable to successfully exploit the Miller Lake island and environments that resulted in high reproductive success. Other local breeding Anatidae because of behavioral constraints were unable to exploit the same situation.
No abstract available.
No abstract available.
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No abstract available.
Habitat selection analyses provide a window into the perceived value of habitats by animals and how those perceptions compare with other animals, change across time, or change in relation to availability (termed functional responses). Habitat selection analysis and functional responses can be used to develop strategies to avoid habitat limitations, guide habitat management, and set attainable conservation goals. GPS relocations of marked animals are the principal data used in habitat selection analysis. The accuracy and frequency with which tracking devices collect data are increasing and may result in non-stationary point processes that result from latent behaviors previously unidentifiable in sparse data.
REMISE OF THE STUDY: Dispersal of parasitic Cuscuta species (dodders) worldwide has been assumed to be largely anthropomorphic because their seeds do not match any previously known dispersal syndrome and no natural dispersal vectors have been reliably documented. However, the genus has a subcosmopolitan distribution and recent phylogeographic results have indicated that at least18 historical cases of long-distance dispersal (LDD) have occurred during its evolution. The objective of this study is to report the first LDD biological vector for Cuscuta seeds. METHODS: Twelve northern pintails ( Anas acuta ) were collected from Suisun Marsh, California and the contents of their lowest part of the large intestine (rectum) were extracted and analyzed. Seed identification was done both morphologically and using a molecular approach. Extracted seeds were tested for germination and compared to seeds not subjected to gut passage to determine the extent of structural changes caused to the seed coat by passing through the digestive tract. KEY RESULTS: Four hundred and twenty dodder seeds were found in the rectum of four northern pintails. From these, 411 seeds were identified as Cuscuta campestris and nine as most likely C. pacifica . The germination rate of C. campestris seeds after gut passage was 55%. Structural changes caused by the gut passage in both species were similar to those caused by an acid scarification. CONCLUSIONS: Endozoochory by waterbirds may explain the historical LDD cases in the evolution of Cuscuta . This also suggests that current border quarantine measures may be insufficient to stopping spreading of dodder pests along migratory flyways.
Hematologic parameters were studied in giant Canada geese ( Branta canadensis maxima ), mallard ducks ( Anas platyrhynchos platyrhynchos ) and various species of diving ducks at seasonal intervals throughout the year. Highest values for packed cell volume, hemoglobin content and erythrocyte counts were found in the winter and pre-nesting periods. Mean corpuscular volume and mean corpuscular hemoglobin varied inversely with these values.