Diving Patterns of Cormorants Phalacrocoracidae

updated on 18-03-2002

Diving Patterns of Cormorants Phalacrocoracidae

after
J. Cooper

published in:
IBIS 1986, vol. 128, pages 562-570

prepared by
Christine Costello
Boston, USA

updated by
Christine Costello - Boston, USA
Stefano Volponi - Dept. of Biology - University of Ferrara, Italy

Dive and rest periods and dive/rest ratios for populations of 20 taxa, representing 18 species of cormorants, in approximate order of increasing mass, are given in Table 1. Mean dive periods range from 6-68 s, but most species fall within the range 20-40 s. Cormorants diving in shallow water or on surface-shoaling fish have relatively short dive periods. (Table 1) Rest periods are shorter than dives but are more variable in duration (higher standard deviations) and means vary from 2.9 to 26.4 s. Dive/rest ratios range from 1.09 to 4.36. Longest mean rest period and smallest dive/rest ratio were obtained for Bank Cormorants Phalacrocorax neglectus gathering seaweed for nest material. Discounting these, the longest mean rst period measured was 23.2 s for foraging Pelagic Cormorants P. pelagicus.

TABLE 1: DIVING PATTERNS OF CORMORANTS PHALACROCORACIDAE
	diving period(s)				resting period(s)
locality	mean	s.d.	range	n	mean	s.d.	range	n
Reed Cormorant, *P. africanus*
Lake Malawi, Malawi	16.7	9.4	8.2-43.4	30
Southwestern Cape, S. Africa	12.5	6.1	2.3-27.1	26	4.3	2.3	1.3-8.7	25
Lake St. Lucia, S. Africa	9*	0.8	3-18	41
			18-34	8
Little Pied Cormorant, *P. melanoleucos*
New Zealand	16			726	7			851
Crowned Cormorant, *P. coronatus*
Southwestern Cape, S. Africa	23.5	8.8	6.7-58.5	142	8.1	4.1	3.0-20.0	51
Pygmy Cormorant, *P. pygmaeus*
			19-42	8
Javanese Cormorant, *P. niger*
			21-38	11
Cape Cormorant, *P. capensis*
Southwestern Cape, S. Africa	24.0				3	7.7
Spotted Cormorant, *P. punctatus*
New Zealand	30			31	12			32
Red-legged Cormorant, *P. gaimardi*
Isla Mazorca, Peru	25.6	17.8	4-71	69
Olivaceous Cormorant, *P. olivaceus*
Texas, USA	6.3*			1348	3.0
Callao. Peru	12.3	4.5	6-27	36
ADULTS
Texas, USA (Loc. 1)	15.3*			435	5.5
Texas, USA (Loc. 2)	6.5*			399	2.9
IMMATURES
Texas, USA (Loc. 1)	17.8*			338	5.5
Texas, USA (Loc. 2)	6.0*			949	3.1
European Shag, *P. aristotelis*
Scotland, Clyde Sea	27.7		max 50	531	9.7
Scotland	40		5-100	155	15		5-40	---
Skomer, Wales	38.4	7.8	19.9-50.8	50	14.5/td>		7.3-26.4	30
Guanay Cormorant, *P. bougainvillii*
Isla Mazorca, Peru	-9.6**	4.5		144
Isla Mazorca, Peru	32.9	22.2		16
Pied Cormorant, *P. varius*
New Zealand	31			841	12			851
Pelagic Cormorant, *P. pelagicus*
Britsh Columbia, Canada	31.3			65	14.3			65
	45.3	1.4(s.e.)	23.7-60.4	44	23.2	1.2(s.e.)	8.5-35.1	44
ADULTS	34.9	4.1		1328	15.2	3.2		460
IMMATURES	35.5	7.8		474	16.9	3.9		190
Double-crested Cormorant, *P. auritus*
Nova Scotia, Canada	25.1			86	10.3			6
New York, USA	20.7	4.3	10-28	55
Bank Cormorant, *P. neglectus*
Southwestern Cape, S. Africa	44.9	7.8	25.5-63.8	157	20.6	8.9	10.6-61.8	137
	28.8+	8.1	17.0-37.8	14	26.4	17.6	8.0-68.2	13
Imperial Cormorant, *P. atriceps*
Marion Island	40.2	13.1	18-88	85	15.0	8.9	2-54	62
CroZet Island	68		45-95	6
European Cormorant, *P. c. carbo*
Scotland	32.6		max 71	461	11.7
Nova Scotia, Canada	51.0			34	13.9			34
Black Cormorant, *P. c. novaehollandiae*
New Zealand	21*			135	7			136
White-breasted Cormorant, *P. c. lucidus*
Lake St. Lucia, S. Africa	14*	1.3	4-30	26
Southwestern Cape, S. Africa	39.2	8.6	18.5-53.5	54	9.0	4.0	2.5-17.5	51
Brandt's Cormorant, *P. penicillatus*
	42			18
Socotran Cormorant, *P. nigrogularis*
				24-51
Notes: * In shallow water (< 2m.) ** Shallow dives on Anchoveta Engraulis ringens shoals (Duffy 1983a) + Nest material (seaweed) gathering and not included in Figures 1-4; all other dives are assumed to be of foraging birds.