Foraging behavior of redheads (Aythya americana) wintering in Texas and Louisiana

Abstract

Redheads, Aythya americana, concentrate in large numbers annually in traditional wintering areas along the western and northern rim of the Gulf of Mexico. Two of these areas are the Laguna Madre of Texas and Chandeleur Sound of Louisiana. We collected data on 54,340 activities from 103 redhead flocks in Texas and 51,650 activities from 57 redhead flocks in Louisiana. Males and females fed similarly, differing neither in levels of feeding (percent of all birds in flock that were feeding) (p>0.90) nor in percentages of birds feeding by diving, tipping, dipping, or gleaning from the surface (p>0.10). The foraging level of redheads in the upper Laguna Madre region was relatively constant throughout two winters. Foraging of redheads in early winter in Louisiana was significantly greater than redhead foraging in the upper Laguna Madre, but by late winter, foraging by redheads in Louisiana had declined to the same level as that shown by redheads foraging in the upper Laguna Madre. The overall foraging level of redheads from Chandeleur Sound was greater (41%) than that of redheads in the upper Laguna Madre (26%), yet it was quite similar to the 46% foraging level reported for redheads from the lower Laguna Madre. Redheads in the upper Laguna Madre region of Texas fed more by diving than did those in the Chandeleur Sound and the lower Laguna Madre. Diving increased in frequency in late winter. Greater reliance by redheads on diving in January and February indicates that the birds altered their foraging to feed in deeper water, suggesting that the large concentrations of redheads staging at this time for spring migration may have displaced some birds to alternative foraging sites. Our results imply that the most likely period for food resources to become limiting for wintering redheads is when they are staging in late winter.

Wintering Behavior of Tundra Swan, Cygnus columbianus, at a Small Water-level Controlled Lake in the Middle and Lower Yangtze River Floodplain

“…The hydrological variation affects the number and distribution of waterbirds (Hua et al, 2009) and their wintering behavior, especially foraging and swimming. Thus, water level is an important influencing factor (Woodin and Michot, 2006). Since the variation of water level affects bathing, pluming and translocation of Tundra swans, the behavior of translocation and maintenance showed obvious changes with the water level in this study.…”

Diurnal time-activity budgets of redheads (Aythya americana) wintering in seagrass beds and coastal ponds in Louisiana and Texas

“…The nutritional quality and belowground biomass of Halodule during the wintering period was similar for Louisiana and Texas (Cornelius, 1975;Michot & Chadwick, 1994;Mitchell et al, 1994;Onuf, 1996;Michot, 1997), so it is unlikely that redheads in Louisiana had to spend more time extracting rhizomes from the substrate. In fact, redheads in Louisiana spent less time feeding by diving, as opposed to tipping and dipping, than redheads in Texas (Woodin & Michot, 2006), so the Louisiana birds would realize savings in energy and time by feeding in shallower waters. Average continuous patch size of Halodule wrightii was smaller at Chandeleur Sound (mean=20 m, max=152 m, along transects perpendicular to shoreline; T. C. Michot & H. A. Neckles, unpublished data) than at the Laguna Madre, where typical Halodule patches were virtually continuous across the entire bay, or along a side, for hundreds of meters (Onuf, 1996).…”

“…FEED included all feeding behaviors identified by Mitchell et al (1992) (i.e., head dip, dive, tip, glean, and peck) and waddle, a behavior very infrequently observed where the birds moved their feet under water along the substrate in a waddling fashion, apparently to expose submerged shoalgrass rhizomes. In a separate paper (Woodin & Michot, 2006) we reported on differences among feeding behaviors. The SWIM category included swim and alert swim.…”

Effect of water level fluctuations on temporal-spatial patterns of foraging activities by the wintering Hooded Crane (Grus monacha)

“…The daily food requirements of birds depend on time budget, activity level, assimilation efficiency and the amount of energy contained in food [6]. Time-activity budgets of waterbirds in the winter could provide data on differential habitat use, evaluate responses of waterbirds to environmental conditions, make inferences about energy budgets and compare populations at different stages during the winter [55,56]. To study the behavioral patterns and time budgets for understanding the changes of habitat use, energy requirement and seasonal variation is of great importance [42].…”

“…Predilection of habitat type and water depth and the shift of diet for waterbirds all can be caused by the availability of food resources [1]. Foraging frequency, length of time spent on foraging and foraging success can reflect the effect of water level fluctuations and the foraging efficiency of waterbirds [56]. The stages of the water level have significantly impacted the foraging behavior of the Hooded Crane.…”