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

Abstract

Diurnal time-activity budgets were determined for wintering redheads (Aythya americana) from estuarine seagrass beds in Louisiana (Chandeleur Sound) and Texas (Laguna Madre) and from ponds adjacent to the Laguna Madre. Activities differed (p<0.0001) by location, month, and diurnal time period. Resting and feeding were the most frequent activities of redheads at the two estuarine sites, whereas drinking was almost nonexistent. Birds on ponds in Texas engaged most frequently in resting and drinking, but feeding was very infrequent. Redheads from the Louisiana estuarine site rested less than birds in Texas at either the Laguna Madre or freshwater ponds. Redheads in Louisiana fed more than birds in Texas; this was partially because of weather differences (colder temperatures in Louisiana), but the location effect was still significant even when we adjusted the model for weather effects. Redheads in Louisiana showed increased resting and decreased feeding as winter progressed, but redheads in Texas did not exhibit a seasonal pattern in either resting or feeding. In Louisiana, birds maintained a high level of feeding activity during the early morning throughout the winter, whereas afternoon feeding tapered off in mid-to late-winter. Texas birds showed a shift from morning feeding in early winter to afternoon feeding in late winter. Males and females at both Chandeleur Sound and Laguna Madre showed differences in their activities, but because the absolute difference seldom exceeded 2%, biological significance is questionable. Diurnal time-activity budgets of redheads on the wintering grounds are influenced by water salinities and the use of dietary fresh water, as well as by weather conditions, tides, and perhaps vegetation differences between sites. The opportunity to osmoregulate via dietary freshwater, vs. via nasal salt glands, may have a significant effect on behavioral allocations.

Benthic Macrophyte Distribution and Abundance in Estuarine Mangrove Lakes and Estuaries: Relationships to Environmental Variables

“…Additionally, the high productivity of SAV beds supports complex aquatic food webs (Fry and Parker 1979;Moncrieff et al 1992) and, in shallow areas, also provides critical seasonal energy sources for migratory waterfowl (Noordhuis et al 2002;Michot et al 2008). Many aquatic and estuarine ecosystems, once characterized by SAV abundance and a clear water column, have experienced regime shifts or changes in stable state to ecosystems characterized by phytoplankton dominance and increased turbidity (Orth and Moore 1983;Scheffer et al 1993).…”

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“…Similar methods have been often used to study the behaviour of numerous species of wetland birds (Tacha 1988), including waterfowl (Poulton et al 2002, Michot et al 2006, Crook 2007, Crook et al 2009). Field observations were conducted from January 2012 to January 2013 during daylight hours.…”

Coastal Pond Use by Redheads Wintering in the Laguna Madre, Texas

“…In particular, the Laguna Madre is the primary wintering area for about 80% of the continental redhead population (Weller 1964;Michot 2000). This large concentration of redheads spends much of the nonbreeding season along the lower Texas coast, usually arriving in mid-October and remaining until early March (Kiel 1957;Custer et al 1997;James 2006) where they forage primarily on shoalgrass rhizomes (Michot et al 2008;D. James, unpublished data).…”

“…Hence, to maintain osmotic equilibrium from ingestion of high salt loads while foraging in the Laguna Madre, redheads make daily flights to adjacent freshwater sources (Kiel 1957;Mitchell et al 1992;Woodin 1994;Adair et al 1996;Michot et al 2006). However, the semi-arid climate and unpredictable precipitation events in this region result in great annual variability in the proportion and distribution of inundated basins (Brown et al 1977).…”