The Company of Biologists

Table 2.

Kinetics of change in δ¹³C_breath values over the course of the experiment for rufous (S. rufus) and Anna's (C. anna)hummingbirds

Bird	ID	Sex	k_i (min^-1)	k_d (min^-1)	f_exo
S. rufus
	N43975	F	0.007	0.135	0.61
	N43978	F	0.162	0.092	1.01
	N44063	M	0.105	0.132	0.96
	N44064	M	0.009	0.077	0.75
	Mean ± s.d.		0.071±0.076	0.109±0.029	0.83±0.18
C. anna
	N44016	M	0.061	0.053	0.94
	N44021	M	0.002	0.059	0.46
	N44040	F	0.071	0.059	1.03
	Mean ± s.d.		0.045±0.037	0.057±0.004	0.81±0.31

Bird	ID	Sex	k_i (min^-1)	k_d (min^-1)	f_exo
S. rufus
	N43975	F	0.007	0.135	0.61
	N43978	F	0.162	0.092	1.01
	N44063	M	0.105	0.132	0.96
	N44064	M	0.009	0.077	0.75
	Mean ± s.d.		0.071±0.076	0.109±0.029	0.83±0.18
C. anna
	N44016	M	0.061	0.053	0.94
	N44021	M	0.002	0.059	0.46
	N44040	F	0.071	0.059	1.03
	Mean ± s.d.		0.045±0.037	0.057±0.004	0.81±0.31

k_i, fractional rate of isotope incorporation into pool of expired CO₂; k_d, fractional rate of isotope disappearance from pool of expired CO₂; f_exo,proportion of expired CO₂ derived from oxidation of cane sugar[during period of availability of cane sucrose solution whenδ ¹³C_breath values had reached a plateau (defined as period beginning 40 min after first feeding on cane sucrose)].

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