The breeding biology of Rose-ringed Parakeets Psittacula krameri in England during a period of rapid population expansion

Figures & data

Table 1. A summary of tree species used as nest sites by Rose-ringed Parakeets.

Genus	Common Name	Used by parakeets
Acer	Maple	8 (11.6%)
Cedrus	Cedar	1 (1.4%)
Fagus	Beech	1 (1.4%)
Fraxinus	Ash	23 (33.3%)
Juglans	Walnut	1 (1.4%)
Platanus	Sycamore	4 (5.8%)
Populus	Poplar	6 (8.7%)
Quercus	Oak	15 (21.7%)
Robinia	Locust	1 (1.4%)
Salix	Willow	2 (2.9%)
Tilia	Lime	5 (7.2%)
Ulnus	Elm	2 (2.9%)
	Total	69 (100%)

Table 2. A summary of the GLM predicting clutch size for the environmental variables.

Predictor variable	β ± se	t	P
Intercept	6.9 ± 1.3	5.3	<0.001
Local tree basal area	−0.001 ± 0.002	−0.5	0.62
Local tree stem count	0.016 ± 0.026	0.6	0.53
Tree height	−0.063 ± 0.033	−1.9	0.07
Orientation	0.002 ± 0.001	1.3	0.20
Nest height	0.053 ± 0.070	0.8	0.45
DBH	−0.002 ± 0.008	−0.3	0.79
Cavity – woodpecker	−1.2 ± 0.4	−2.8	0.008
Cavity – nestbox	−0.45 ± 0.53	−0.9	0.40
Occupied two years	0.37 ± 0.47	0.8	0.44
Occupied three years	0.60 ± 0.64	0.9	0.36
Subadult	−0.25 ± 0.55	−0.5	0.65
Southeastern London	0.19 ± 0.51	0.4	0.71
Studland	−1.8 ± 1.0	−1.8	0.08
Isle of Thanet, Kent	0.048 ± 0.62	0.1	0.94
Date of first egg	−0.018 ± 0.011	−1.6	0.12