The ecology of Black Guillemot Cepphus grylle grylle chicks in the Baltic Sea region: insights into their diet, survival, nest predation and moment of fledging

Figures & data

Figure 1. The Baltic study sites delineated by circles. The photograph shows one of the islands.

Figure 2. Example of a picture taken by a camera trap, showing a Black Guillemot returning to the nest with a Viviparous Eelpout.

Table 1. Summary of breeding parameters of Black Guillemots.

	2014	2015	Mean
Total number of nests found	36	31	33.5
Total number of eggs found	62	45	53.5
Mean number of eggs per nest	1.7	1.5	1.6
Total number of eggs hatched	55	33	44
Hatching success	0.89	0.73	0.81
Total number of young likely fledged	52	32	43
Perceived fledgling success	0.95	0.97	0.98
Total number of dead adults found	1	3	2
Total number of dead juveniles found	1	1	1
Total number of adults ringed	9	5	7
Total number of juveniles ringed	48	24	36
Mean weight of adults (g)	357 (102)	424 (42)	388 (85)
Mean wing length of adults (mm)	176 (3)	173 (3)	175 (3)

Note: Standard deviations are shown in brackets.

Figure 3. Weight change of Black Guillemot nestlings against age (days after hatching) for five nestlings from three nests (1, 2 and 3).

Table 2. Estimated hatching and fledging dates for Black Guillemots at each nest and for each nestling.

Camera	Juvenile	Hatching date	Fledging day	Number of days in the nest
1	1	11–06–2014	17–07–2014	36
1	2	11–06–2014	Disappeared
2	1	11–06–2014	19–07–2014	38
2	2	11–06–2014	Disappeared
3	1	17–06–2014	19–07–2014	32
3	2	17–06–2014	20–07–2014	33
4	1	26–06–2014	31–07–2014	35
4	2	26–06–2014	31–07–2014	35
5	1	23–06–2014	30–07–2014	37
6	1	19–06–2014	After 17–07–2014	>28
6	2	19–06–2014	After 17–07–2014	>28