Using priority to food access: fattening strategies in dominance-structured willow tit (Parus montanus) flocks

Long-term trend toward earlier breeding in an American bird: A response to global warming?

“…Experimental insulation of nest boxes caused great tits to lay earlier in the spring than controls (37), suggesting that cold temperatures at night critically affect laying dates. Passerine birds commonly lose nearly 10% of their body mass over cold nights (38)(39)(40), and we have confirmed this for free-ranging Mexican jays using electronic, self-weighing scales (J.L.B., unpublished work). Thus, two plausible environmental mechanisms exist for a trend to warmer minimum temperatures in early spring to cause earlier breeding in birds, namely by leading to earlier emergence of insect food for the female and her nestlings and by energy savings for females on cold nights.…”

Correlates of behavioural dominance in mallards and American black ducks

“…In some species, body mass is positively correlated with dominance (e.g. bar-headed goose, Anser indicus : Lamprecht 1986), but in other species dominant birds tend to be lighter than subordinates (dark-eyed junco, Junco hyemalis: Cristol 1992; willow tit, Parus montanus: Ekman & Lilliendahl 1993). The change in relationship between body mass and dominance in our study may be a result of loss in body mass between the winter and spring trials.…”

Attracting and capturing Coal TitsParus ater:Biases associated with the use of tape lures

“…As transients, individuals have to cope with unknown conditions, become subordinates to resident individuals (Ekman 1989, Sandeli andSmith 1991) and furthermore, they have limited possibilities to hoard food (Ekman 1989). Consequently, increased fat levels may enable dispersing birds to cope with variable food availability (Blem 1990, Ekman andLilliendahl 1993). In a concurrent study in the same area, during winter, resident juvenile birds had also lower fat indexes than those which abandoned the area and were not recaptured, thus becoming transients.…”