The response of Grey Herons Ardea cinerea to changes in prey abundance

Figures & data

Figure 1. Study area with the colony in Mosty (black point) and the main foraging areas (FAs) of Grey Herons Ardea cinerea (broken line ovals; FA1, Reda River Valley including wet meadows, canals and the river mouth; FA2, the Gulf of Gdańsk coastal area including shallow coastal water and wet meadows).

Table 1. Relative abundance (undigested and partly digested fish combined) and biomass (only undigested fish) of regurgitated fish collected in the Grey Heron Ardea cinere a colony in Mosty in 2000–02 and 2008–09.

Prey item	Abundance (%)		Biomass (%)
	2000–02	2008–09	2000–02	2008–09
Round Goby Neogobius melanostomus	94.9*	55.6*	99.5**	37.8**
Three-spined Stickleback Gasterosteus aculeatus	4.0**	23.3**	0.3**	2.7**
Other fish	1.1**	21.1**	0.1**	59.5**
n	176	90	86	56
χ ^2 test: *P < 0.01; **P < 0.0001.

Figure 2. Body length classes of fish (all species combined) found in the colony of Grey Herons Ardea cinerea in Mosty in 2000–02 and 2008–09 (undigested regurgitated) and 2009 (Sea Trout tagged in 2009; length measured when they were tagged).

Table 2. Body length and biomass of regurgitated, undigested and partly digested fish found in the colony of Grey Herons Ardea cinerea in Mosty in 2000–02 and 2008–09 (undigested regurgitated).

Prey item	Value	Length (mm)		Biomass (g)
		2000–02	2008–09	2000–02	2008–09
Undigested
Round Goby Neogobius melanostomus	Median	110 ^ns	100 ^ns	20.7 ^ns	14.8 ^ns
	Q1–Q3	95–130	85–120	12.4–37.1	8.4–28.0
	Min–max	70–180	65–200	4.3–115.4	3.3–166.7
	n	82	30	82	30
All fish species combined	Median	107.5*	90.0*	19.1**	10.2**
	Q1–Q3	95–120	70–130	12.4–28.0	4.3–26.1
	Min–max	55–180	55–290	1.8–115.3	1.8–310.8
	n	86	59	86	56
Partly digested
All fish species combined	Median	100 ^ns	90 ^ns	–	–
	Q1–Q3	90–120	75–120	–	–
	Min–max	55–360	30–240	–	–
	n	75	30	–	–
Mann–Whitney U-test: *P < 0.05; **P < 0.005; ^ns P > 0.05.

Table 3. Frequency of pellets of Grey Herons Ardea cinerea containing different mammalian taxa (identified by bone remains/hair) in 2000–02 (Jakubas & Mioduszewska 2005) and 2008–09.

Prey item	% (identified by bones)		% (identified by hair)
	2000–02	2008–09	2000–02	2008–09
Apodemus sp.	0	0	0	9
Apodemus sylvaticus	0	0	0	3
Apodemus agrarius	0	0	0	26
Arvicola terrestris	11***	3***	42^ns	60^ns
Clethrionomys glareolus	0	0	3	3
Glis glis	0	0	0	6
Microtus sp.	4***	14***	77^ns	63^ns
Microtus agrestis	0	0	0	17
Microtus oeconomus	0	0	0	14
Muridae	0	0	0	3
Mus musculus	0	0	0	3
Sorex/Neomys	0	0	7	11
Sorex araneus	0	0	0	3
Talpa europaea	3*	6*	47**	6**
Unidentified remains	37	6	0	0
No. pellets analyzed	121	35	108	35
χ ^2 test: *P < 0.05; **P < 0.005; ***P < 0.001; ^ns P > 0.05.

Jakubas , D. and Mioduszewska , A. 2005 . Diet composition and food consumption of the grey heron (Ardea cinerea) from breeding colonies in northern Poland . Eur. J. Wildl. Res. , 51 : 191 – 198 .

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