Table 2.

Factors affecting the production of ‘tää’ calls by willow tits analysed using the generalized linear mixed model. Calling behaviour (yes or no) was modelled in response to the number of repeated visits to the feeder, subsequent foraging behaviour (consume or cache), and presence or absence of flock members. s.e.: standard error. Sample size: n = 381 feeder visitations by 13 individuals in 41 trials. All fixed terms were standardized before the analysis.

model	estimate	s.e.	d.f.	χ2	p
intercept	−2.67	0.44
number of feeder visitations	0.97	0.21	1	7.52	<0.01
flock members (presence/absence)	−0.64	0.25	1	15.33	<0.001
subsequent foraging behaviour (consume/cache)	−0.86	0.26	1	25.21	<0.001