Population Energetics of Northern Pintails
Wintering in the Sacramento Valley, California

Table 1

Table 1. Daily energy expenditure (DEE; kJ/day), daily energy required from body reserves (DER_res; kJ/day), daily energy obtained from food (DER_food; kJ/day), and food intake (g dry mass/day) of individual adult male and female northern pintails from wetlands and rice fields (Rice) during a dry (1980-81) and a wet (1981-82) winter in the Sacramento Valley, California.
Period^b	Sex	Dry winter (1980-1981)						Wet winter (1981-1982)
		DEE	DER_res	DER_food^a		Food intake (g)		DEE	DER_res	DER_food		Food intake (g)
		DEE	DER_res	Wetlands	Rice	Wetlands	Rice	DEE	DER_res	Wetlands	Rice	Wetlands	Rice
Aug-Sep	M	794	3	791	0	56	0	836	4	832	0	59	0
Aug-Sep	F	786	0	786	0	56	0	700	8	692	0	49	0
Sep-Oct	M	1,003	0	1,003	0	74	0	976	0	976	0	72	0
Sep-Oct	F	860	0	860	0	64	0	804	0	804	0	60	0
Oct-Nov	M	1,022	1	255	766	19	53	890	2	222	666	16	46
Oct-Nov	F	1,002	0	250	752	19	52	1,044	0	261	783	19	54
Nov-Dec	M	982	46	47	889	4	61	911	53	43	815	3	56
Nov-Dec	F	912	64	42	806	3	56	881	70	41	770	3	53
Dec-Jan	M	971	116	43	812	3	56	997	0	50	947	4	65
Dec-Jan	F	908	64	42	802	3	55	930	2	46	882	4	61
Jan-Feb	M	1,180	1	59	1,120	5	77	1,136	1	57	1,079	4	74
Jan-Feb	F	998	0	50	948	4	65	956	1	48	907	4	63
Feb-Mar	M	957	39	46	872	4	60	1,032	1	52	979	4	68
Feb-Mar	F	888	54	42	792	3	55	925	0	46	879	4	61
^a Proportion of food energy obtained in August-September and September-October = 100% from wetlands (diurnal); October-November = 25% from wetlands, 75% from rice fields (nocturnal); November-March = 5% wetlands, 95% rice fields (see METHODS and Table 2). ^b Assumes 30 days between monthly midpoints (e.g., Aug-Sep = 15 Aug to 15 Sep).