A flyway perspective of foraging activity in Eurasian Green-winged Teal,Anas crecca crecca

Abstract

Time-activity budgets in the family Anatidae are available for the wintering and breeding periods. We present the first flyway-level study of foraging time in a long-distance migrant, the Eurasian Green-winged Teal, Anas crecca crecca L., 1758 (''Teal''). Behavioral data from early and late spring staging, breeding, and molting sites were collected with standardized protocols to explore differences between the sexes, seasons, and diel patterns. Teal foraging activity was compared with that of the Mallard, Anas platyrhynchos L., 1758 and Northern Shoveler, Anas clypeata L., 1758, and the potential effects of duck density and predator-caused disturbance were explored. In early spring, foraging time was moderate (50.5%) and mostly nocturnal (45%). It increased dramatically in all three species at migration stopovers and during molt, mostly because of increased diurnal foraging, while nocturnal foraging remained fairly constant along the flyway. These patterns adhere to the ''income breeding'' strategy expected for this species. No differences between the sexes were recorded in either species studied. Teal foraging time was positively correlated with density of Teal and all ducks present, but negatively correlated with predator disturbance. Our study suggests that Teal, in addition to being income breeders, may also be considered as income migrants; they find the energy necessary to migrate at staging sites along the flyway.Résumé : Les budgets-temps des Anatidae sont disponibles pour les périodes d'hivernage et de reproduction. Nous pré-sentons la première étude, à l'échelle d'une voie de migration, du temps d'approvisionnement d'un migrateur de longue distance, la sarcelle d'hiver, Anas crecca crecca L., 1758. Les données comportementales de début et fin de migration printanière, reproduction et mue ont été obtenues, avec le même protocole, afin de tester les différences entre sexes, saisons et variations nycthémérales. L'approvisionnement des sarcelles est comparé à celui des canards colverts, Anas platyrhynchos L., 1758, et des canards souchets, Anas clypeata L., 1758; les effets de la densité de canards et du dérangement par les prédateurs sont également testés. Au début du printemps, le temps d'approvisionnement était court (50,5 %), et essentiellement nocturne (45 %). Il augmentait ensuite de façon spectaculaire pour les trois espèces sur les haltes migratoires et durant la mue (principalement à cause de l'approvisionnement diurne, l'approvisionnement nocturne étant constant). Ceci s'accorde avec la stratégie de « reproducteur sur revenu » attendue chez ces espèces. Aucune différence inter-sexe n'a été relevée chez les espèces étudiées. Le temps d'approvisionnement des sarcelles était corrélé positivement avec leur densité et celle de l'ensemble des canards présents et négativement avec le dérangement par les prédateurs. Les sarcelles seraient des reproducteurs mais également des migrateurs sur revenu, trouvant l'énergie nécessaire à leur migration en route.

Hatching in dabbling ducks and emergence in chironomids: a case of predator–prey synchrony?

“…The breeding period of dabbling ducks, however, may not be as easily adapted to seasonal changes in food abundance at the breeding site. One important reason is that any such adaptation has to be traded off against selective pressures acting in other biomes and at other times of the annual cycle (Arzel et al, 2007(Arzel et al, , 2009.…”

Extreme climatic variability during migration invokes physiological and dietary plasticity among spring migrating ducks

“…This result, combined with other metrics, lends further support to the conclusion that Lesser Scaup were burdened with increased energetic demands that they were not able to overcome by the time the late migration progressed in our study area in 2013. These results suggest that Lesser Scaup may conform more to a "capital migrant" strategy (sensu Arzel et al 2007), relying more on carrying a larger balance of lipid reserves acquired during winter (Anteau and Afton 2004;Herring and Collazo 2006) and opportunistically during migration (Esler et al 2001;Anteau and Afton 2009) but less prone to recovering from losses associated with energetically demanding environmental or migration conditions. It is also plausible that forgoing lipid accumulation altogether was a strategy in and of itself among migrating Lesser Scaup during the coldest and latest year to try to minimize possible trade-offs with wing loading or navigation associated with high lipid burdens (Lima 1986), although migrants would still have to meet minimum lipid balances necessary to complete migration and breeding, which tend to limit clutch size and reproduction in Lesser Scaup (Afton and Ankney 1991) and other ducks (Ankney et al 1991).…”

“…Such a diet shift could explain the maintenance of lipids in that year and the concomitant decline in protein because high intake of invertebrate-rich diets has been associated with increases in protein masses in ducks (Alisauskas et al 1990; Barzen and Serie 1990;Alisauskas and Ankney 1994). This adaptive dietary intake to focus on maintaining the same relative reserve of lipids seems consistent with an "income migrant" strategy (sensu Arzel et al 2007) where migrants adjust foraging to meet demands encountered en route rather than relying on stores built up at previous stopovers or wintering areas. Lesser Scaup followed a pattern similar to that of Blue-winged Teal with protein reserves, but all other metrics notably contrasted between the two species.…”

A flyway perspective on food resource abundance in a long-distance migrant, the Eurasian teal (Anas crecca)

“…During the breeding season, however, they have access to an overabundance of boreal lakes, leading to low densities of birds per wetland and to many suitable sites remaining unused (Elmberg et al 2005). In a related study, Arzel et al (2007) found a positive relationship between teal foraging time and densities of both teal and other dabbling ducks. This is consistent with the idea that food is not limiting; alternatively, it could indicate that teal offset costs of higher food competition for benefits of improved predator vigilance and dilution effects provided by larger flocks (Guillemain et al 2002.…”