Windscapes shape seabird instantaneous energy costs but adult behavior buffers impact on offspring

Table 1 Statistical output (F-values with P-values in parentheses) from general linear mixed models, with individual as a random effect, describing six foraging parameters for thick-billed murres and black-legged kittiwakes as a function of year, time of day (circularly-transformed) and windspeed

Parameter	N	Year	Crosswind	Tailwind	Time
Murres
Outbound wing beat frequency	10	2.63 (0.11)	0.22¹ (0.66)	*13.5* ¹ *(0.0004)*	0.05 (0.89)
Flight speed	35	*23.2 (<0.0001)*	3.58 (0.06)	*171.1 (<0.0001)*	0.08 (0.78)
Energy delivery rate between 0600 h and 1000 h EST	82	2.61 (0.11)	6.48 (0.01) ²
Time flying per day	210	2.96 (0.02)	0.06 (0.81)²
Residual of daily energy expenditure on body mass	49	1.53 (0.22)	2.21 (0.14)²
Residual of chick growth rate on age³	720	4.23 (0.04)	0.39 (0.93)²
Kittiwakes
Wing beat frequency	10		0.11 (0.87)	4.67 (0.04)	0.25 (0.61)
Flight speed	10		1.58 (0.22)	*178.9 (<0.0001)*	0.01 (0.98)
Feeding rate between 900 h and 1300 h AKDT	96		4.41 (0.04) ²
Time flying per day	30		0.45 (0.51)²
Residual of daily energy expenditure on body mass	37		0.01 (0.92)²
Residual of chick growth rate on age³	126	0.49 (0.46)	3.94 (0.05)²

¹Actual direction of flight was unknown, so we assumed 101 ± 10° for outbound direction (average from birds equipped with GPS).
²Average wind speed, rather than crosswind and tailwind components, used as independent variable. To account for the confounding effect of date on wind, average windspeed for each day was calculated as residual from the average value for a given date across all 10 years.
³Hatch date (murre: F_1,2876 = 10.9 P = 0.001; kittiwake: F_1,686 = 2.25, P = 0.13) was also included as a covariate.
Values in bold are statistically significant at the P < 0.05 level and values in italics are significant at P < 0.002.

ISSN: 2051-3933