How much to carry? Implications of maximum load carrying capacity for prey use of urban and rural Northern Goshawks Accipiter gentilis

Figures & data

Figure 1. Flight muscles of the left-hand body side of a male Goshawk from a ventral (left) and a dorsal (right) view after skinning, prior to dissection.

Table 1. Different body measurements and parameters calculated for individual male and female Goshawks. TFMM = Total flight muscle mass; MCC = Maximum carrying capacity; MLCC = Maximum load carrying capacity.

Sex	Body mass [g]	TFMM [g]	TFMM/ body mass	MCC [g]	MLCC [g]	MLCC/body mass
m	690	188.8	0.27	1247	557	0.81
m	715	247.0	0.35	1637	922	1.29
m	730	173.8	0.24	1147	417	0.57
m	725	236.4	0.33	1566	841	1.16
f	1040	262.6	0.25	1742	702	0.68
f	1010	279.8	0.28	1857	847	0.84
f	1270	370.3	0.29	2465	1195	0.94
f	1255	360.0	0.29	2396	1141	0.91
$\overline{\mathit{x}}$ (m)	715 ± 18	211.5 ± 35.7	0.30 ± 0.05	1399 ± 239	684 ± 237	0.96 ± 0.33
$\overline{\mathit{x}}$ (f)	1143 ± 137	318.2 ± 54.9	0.28 ± 0.02	2115 ± 368	971 ± 235	0.84 ± 0.12

Figure 2. Proportion of prey by weight classes by means of counts and biomass for the two different environments.

Table 2. Features of breeding season diet for Goshawks at urban and rural study sites.

Habitat type	Sample size (n)	Mean prey weight (g)	Birds (%)		Mammals (%)
			Biomass	Counts	Biomass	Counts
Urban	554	299 ± 161	95.7	98	4.3	2.0
Rural	344	255 ± 221	97.2	95.9	2.8	4.1

Figure 3. Density distribution of prey weights for all six study sites. Dashed (male goshawk, red area) and dotted (female goshawk, blue area) indicate mean maximum additional load, with coloured lines representing standard errors. Pictograms of exemplary prey species are positioned as a reference and according to their body weight.