Do mallard ducks feature in the diet of stoats in an agricultural landscape?

Figures & data

Table 1. Frequency and percent frequency of occurrence for prey items found in the stomachs of 26 stoats caught in Lochiel, Southland, New Zealand between 14 August and 24 November 2016 and 2017.

Prey item	Frequency	Percent frequency (%)
Mallard	1	3.8
Mallard egg	1	3.8
Small bird	7	26.9
Small bird egg	8	30.7
Rodent	4	15.4
Unidentified tissue	7	26.9
Unidentified hair	3	11.5
Invertebrate	1	3.8
Vegetation	6	22.2
Lagomorph	0	0

Figure 1. Isospace plot showing δ¹³C and δ¹⁵N values of stoat livers taken in Lochiel, Southland, in relation to their prey. Values are means ± 1 standard deviation for prey values. Stoat liver values have been corrected using tissue specific trophic enrichment factors.

Table 2. Stable isotope values (δ¹⁵N, δ¹³C) of stoat liver tissue where stoats were captured between 14 August and 24 November 2016 and 2017 in Lochiel, Southland, New Zealand. Values for stoat liver are from lipid extracted tissue.

Stoat sex	Date of capture	δ^15N^Liver	δ^13C^Liver
Female	5/09/2016	12.6	−26.8
Male	5/09/2016	13.2	−26.4
Male	7/09/2016	12.5	−26.3
Male	19/09/2016	12.3	−26.4
Female	22/09/2016	12.3	−26.3
Female	22/09/2016	11.8	−26.9
Female	29/09/2016	13.2	−25.5
Female	3/10/2016	11.3	−27.0
Male	4/10/2016	13.1	−27.2
Male	21/10/2016	10.8	−26.2
Female	22/10/2016	11.1	−26.2
Male	31/10/2016	12.4	−26.5
Female	14/08/2017	13.5	−25.6
Male	11/09/2017	11.4	−26.3
Male	19/09/2017	10.6	−27.1
Male	3/10/2017	13.0	−25.5
Male	9/10/2017	12.4	−26.5
Male	11/10/2017	11.7	−26.0
Male	16/10/2017	12.3	−26.1
Male	24/10/2017	12.4	−26.6
Male	24/10/2017	11.0	−25.9
Female	8/11/2017	11.4	−25.2
Male	8/11/2017	11.2	−26.4
Male	13/11/2017	12.8	−25.5
Female	13/11/2017	13.3	−24.7
Female	24/11/2017	11.2	−25.3

Table 3. Estimated dietary proportions for individual stoats caught during the 2016 and 2017 mallard breeding season at Lochiel, Southland, New Zealand. Values are means ± 1 SD.

Sex	Date of capture	Mallard	Small bird	Bird egg	Rodent	Lagomorph
Female	5/09/2016	0.022 ± 0.067	0.074 ± 0.097	0.84 ± 0.156	0.053 ± 0.075	0.011 ± 0.055
Male	5/09/2016	0.025 ± 0.073	0.082 ± 0.105	0.819 ± 0.171	0.066 ± 0.093	0.009 ± 0.043
Male	7/09/2016	0.026 ± 0.076	0.825 ± 0.159	0.082 ± 0.097	0.057 ± 0.078	0.01 ± 0.048
Male	19/09/2016	0.025 ± 0.075	0.081 ± 0.096	0.83 ± 0.157	0.054 ± 0.071	0.01 ± 0.049
Female	22/09/2016	0.027 ± 0.08	0.081 ± 0.095	0.828 ± 0.158	0.053 ± 0.07	0.011 ± 0.052
Female	22/09/2016	0.023 ± 0.069	0.071 ± 0.088	0.847 ± 0.149	0.046 ± 0.061	0.013 ± 0.063
Female	29/09/2016	0.029 ± 0.083	0.105 ± 0.132	0.779 ± 0.2	0.08 ± 0.112	0.007 ± 0.035
Female	3/10/2016	0.02 ± 0.056	0.065 ± 0.08	0.856 ± 0.149	0.042 ± 0.057	0.017 ± 0.082
Male	4/10/2016	0.021 ± 0.072	0.07 ± 0.101	0.841 ± 0.17	0.058 ± 0.095	0.01 ± 0.051
Male	21/10/2016	0.021 ± 0.063	0.07 ± 0.083	0.849 ± 0.152	0.043 ± 0.06	0.016 ± 0.073
Female	22/10/2016	0.023 ± 0.071	0.074 ± 0.09	0.843 ± 0.152	0.045 ± 0.06	0.014 ± 0.064
Male	31/10/2016	0.025 ± 0.074	0.079 ± 0.095	0.833 ± 0.155	0.053 ± 0.072	0.01 ± 0.047
Female	14/08/2017	0.028 ± 0.083	0.099 ± 0.128	0.779 ± 0.203	0.087 ± 0.123	0.007 ± 0.034
Male	11/09/2017	0.024 ± 0.072	0.076 ± 0.094	0.839 ± 0.154	0.047 ± 0.062	0.014 ± 0.063
Male	19/09/2017	0.017 ± 0.05	0.058 ± 0.078	0.861 ± 0.164	0.039 ± 0.063	0.024 ± 0.106
Male	3/10/2017	0.029 ± 0.083	0.106 ± 0.131	0.783 ± 0.194	0.075 ± 0.102	0.008 ± 0.036
Male	9/10/2017	0.025 ± 0.075	0.08 ± 0.098	0.832 ± 0.155	0.053 ± 0.07	0.01 ± 0.049
Male	11/10/2017	0.027 ± 0.08	0.088 ± 0.107	0.819 ± 0.164	0.056 ± 0.074	0.01 ± 0.045
Male	16/10/2017	0.027 ± 0.078	0.086 ± 0.104	0.825 ± 0.16	0.051 ± 0.067	0.011 ± 0.051
Male	24/10/2017	0.024 ± 0.071	0.077 ± 0.094	0.834 ± 0.154	0.054 ± 0.075	0.011 ± 0.052
Male	24/10/2017	0.024 ± 0.069	0.078 ± 0.093	0.838 ± 0.156	0.046 ± 0.064	0.014 ± 0.064
Female	8/11/2017	0.028 ± 0.086	0.104 ± 0.134	0.806 ± 0.185	0.052 ± 0.073	0.01 ± 0.046
Male	8/11/2017	0.022 ± 0.066	0.072 ± 0.087	0.847 ± 0.152	0.044 ± 0.061	0.015 ± 0.068
Male	13/11/2017	0.029 ± 0.084	0.106 ± 0.132	0.787 ± 0.19	0.069 ± 0.097	0.008 ± 0.037
Female	13/11/2017	0.03 ± 0.092	0.139 ± 0.186	0.728 ± 0.249	0.097 ± 0.14	0.007 ± 0.031
Female	24/11/2017	0.027 ± 0.083	0.094 ± 0.123	0.819 ± 0.176	0.049 ± 0.071	0.011 ± 0.049

Table

Prey item	δ^15N	δ^13C	δ^13C^Lipid normalised
Mallard hen (n = 8)	8.7 ± 0.2 (7.7, 9.6)	−27.6 ± 0.3 (−29.2, −26.7)	−26.8 ± 0.3 (−28.2, −25.9)
Mallard duckling (n = 5)	8.8 ± 0.4 (7.7, 9.6)	−27.5 ± 0.3 (−28.1, −26.7)	−26.5 ± 0.3 (−27.1, −25.7)
Mallard (mallard hen and duckling combined) (n = 13)	8.7 ± 0.2 (7.7, 9.6)	−27.6 ± 0.2 (−29.2, −26.7)	−26.7 ± 0.2 (−28.2, −25.7)
Small bird (n = 7)	9.00 ± 0.3 (8.00, 9.9)	−26.4 ± 0.3 (−27.6, −24.6)	−25.5 ± 0.3 (−26.3, −23.8)
Small bird egg (n = 5)	8.8 ± 0.4 (7.9, 9.9)	−27.1 ± 0.1 (−27.3, −26.9)
Mallard egg (n = 5)	8.5 ± 0.2 (7.9, 9.2)	−27.4 ± 0.2 (−28.0, −26.9)
Egg (mallard egg and small bird egg combined) (n = 10)	8.6 ± 0.2 (7.9, 10.0)	−27.3 ± 0.1 (−28.00, −26.9)
Rat (n = 4)	11.4 ± 1.2 (9.00, 14.6)	−27.5 ± 0.5 (−28.4, −26.00)	−25.1 ± 0.3 (−25.6, −24.8)
Mouse (n = 3)	12.00 ± 1.6 (8.9, 14.4)	−27.0 ± 0.1 (−27.3, −26.8)	−25.1 ± 0.3 (−25.7, −24.8)
Rodent (rat and mouse combined) (n = 7)	11.7 ± 0.9 (8.9, 14.6)	−27.3 ± 0.3 (−28.4, −26.0)	−26.0 ± 0.5 (−27.6, −24.8)
Hare (n = 3)	5.9 ± 1.1 (4.6, 7.9)	−30.0 ± 0.3 (−30.4, −29.3)	−28.9 ± 0.3 (−29.7, −28.9)
Rabbit (n = 2)	5.2 ± 0.04 (5.1, 5.2)	−29.0 ± 0.01 (−29.0, 29.0)	−28.3 ± 0.002 (−28.3, −28.3)
Lagomorph (hare and rabbit combined)	5.6 ± 0.6 (4.3, 7.9)	−29.6 ± 0.3(−30.4, −29.0)	−28.7 ± 0.2 (−29.4, −28.3)