Table 1.

Results of model selection of linear mixed models to investigate specific hypotheses predicting Hb concentration. Hct, haematocrit; EM, elevational migrant (1, 0); mass, mass of the individual (in grams); range, elevational range (in metres); range position, proportion of range where sampled; elevation, elevation at which sampled; upper limit, highest limit of elevational distribution. X indicates predictors used as fixed effects in the model. Species was used as a random intercept effect in all models. All models include an interaction between the two variables in the model. Models are arranged from models showing highest fit to models showing lowest fit.

model no.	Hct	EM	mass	range	elevation	upper limit	range position	d.f.	ΔAICc
3	X	X						6	0
4	X					X		6	12.33
6	X			X				6	14.39
2	X				X			6	17.73
9	X						X	6	22.2
1	X	X	X	X	X	X	X	11	27.66
5					X	X		6	33.84
10					X		X	6	35.81
7				X		X		6	37.22
8			X	X				6	37.79