Read on Twitter
Our new paper with @ConnorEcology is now (online early) in @IBIS_journal - A thread
Sex and age differences in the diet of the Eurasian Sparrowhawk using web-sourced photographs: exploring the feasibility of a new citizen science approach
https://onlinelibrary.wiley.com/doi/10.1111/ibi.12918
#ornithology
Sex and age differences in the diet of the Eurasian Sparrowhawk using web-sourced photographs: exploring the feasibility of a new citizen science approach
https://onlinelibrary.wiley.com/doi/10.1111/ibi.12918
#ornithology
We obtained nearly 850 photos of sparrowhawks on prey from throughout the UK - mainly from @BirdGuides @Facebook @Twitter and using the Morphic App
https://besjournals.onlinelibrary.wiley.com/doi/full/10.1111/2041-210X.12562
- we identified prey to species level in C. 85% of photos - for other prey we identified them by size
https://besjournals.onlinelibrary.wiley.com/doi/full/10.1111/2041-210X.12562
- we identified prey to species level in C. 85% of photos - for other prey we identified them by size
We then enlisted the help of expert ornithologists to confirm ages and sexes of each hawk, including @_robsheldon @stevedudley_ @ronniegraham4 @Au_Erithacus @wyliehorn @ddbirder @EllenrWilson @nomadbirder @Michael86260085 @GrafhamWBirder @zephyrbirds @BoyWonderBirder @RuthTingay
From 843 photos, 568 (67%) were adults. Of the adult photos, 312 (55%) were males and 256 (45%) were females. There were 275 photos of juveniles and of these 96 (35%) were males and 179 (65%) females
Overall, we identified 46 different avian species in the diet
Overall, we identified 46 different avian species in the diet
Relatively few prey types featured frequently in the adult diet, with only 8 prey types comprising > 5% of prey: Wood Pigeon, Collared Dove, Rock Dove, Blackbird, Starling, House Sparrow & two size classes of unidentified birds (small and medium).
Combined =76% of adult diet
Combined =76% of adult diet
There were 12 prey items that had a frequency ≥ 10; for these species, we examined statistical differences between the sexes and ages. Significant differences were found for eight of these 12 key prey items between either sex, or age, or an interaction between sex and age
Adult female sparrowhawks preyed on items that were around 2.5 times heavier than those of adult males. However, for juvenile birds, the difference between the sexes was not as great, with females preying on items around 1.5 times heavier than males
We explored whether our approach may have a size bias e.g. large items might be photo'd more often if they take longer to process. To explore this we watch videos of hawks processing prey - timing the different stages, & also looked at the proportion of these stages in our photos
This work builds on this paper - where we used a similar approach to look at the diet of Martial Eagles
https://academic.oup.com/condor/article/121/1/duy015/5318747?login=true
We believe this approach can be used for many other raptor species and can overcome some of the limitations of other methods used to study raptor diet
https://academic.oup.com/condor/article/121/1/duy015/5318747?login=true
We believe this approach can be used for many other raptor species and can overcome some of the limitations of other methods used to study raptor diet
