Mark–resight approach as a tool to estimate population size of one of the world's smallest goose populations

Figures & data

Table 1. Seasonal survival rates and associated unpublished standard deviations from Clausen et al. (2001), and mark–resight estimates from the current study of East-Atlantic Light-bellied Brent Geese.

Season	Estimate	sd	95% LCL	95% UCL
Spring to autumn	0.914	± 0.016	0.877	0.940
Autumn to winter	0.996	± 0.016	0.960	1.000
Winter to spring (cold winter)	0.973	± 0.012	0.937	0.989
Winter to spring (normal winter)	0.907	± 0.033	0.802	0.954
Parameter	Estimate	n	95% LCL	95% UCL
R (Mågerodde)	25.88	14	24.80	26.96
R (Agerø)	160.05	18	147.50	172.59
R (Total)	68.21	36	65.69	70.74
M	115	200	114	116
N	7845		7245	8438
M, number of ringed birds alive during the study period (see Table 2); R, ratio of total to marked geese in the population; N, estimated total population size; n, number of screened flocks when calculating R, and the number of simulations used to estimate M; LCL, lower confidence limit; UCL, upper confidence limit.

Table 2. Number of ringed birds, annual survival rates, estimated number of surviving ringed birds and total population counts of the East-Atlantic flyway population of Light-bellied Brent Geese 1986/87–2008/09. The annual estimate of ringed birds alive in any given year is estimated from the stochastic model described in the text.

Season	Number of individuals ringed	Estimated ringed birds alive in spring	Winter condition	Population count
1986/87	1	1	Cold	3800
1987/88	3	4	Cold	4500
1988/89	0	3	Normal–mild	5600
1989/90	10	13	Normal–mild	4400
1990/91	69	81	Normal–mild	5150
1991/92	64	135	Normal–mild	4200
1992/93	0	120	Normal–mild	4000
1993/94	31	137	Normal–mild	5800
1994/95	11	132	Normal–mild	5400
1995/96	69	178	Cold	4450
1996/97	104	262	Normal–mild	5500
1997/98	2	234	Normal–mild	6050
1998/99	0	207	Normal–mild	5100
1999/00	0	184	Normal–mild	5900
2000/01	78	241	Normal–mild	6600
2001/02	0	213	Normal–mild	6500
2002/03	0	189	Normal–mild	6469
2003/04	0	167	Normal–mild	6405
2004/05	1	149	Normal–mild	7637
2005/06	42	165	Cold	6185
2006/07	0	146	Normal–mild	7180
2007/08	0	130	Normal–mild	7126
2008/09	0	115	Normal–mild	7600