I thought I’d focus on Leg ‘o’ Mutton which we were lucky enough to be awarded the conservation management contract for last autumn. In particular I will focus on the resident Tawny Owls (Strix aluco).
Tawny owls are synonymous with the classic nocturnal ‘twit -twoo’. However, this is most often the territorial call of the male through autumn and winter. The female tawny owl is responsible for the ‘keeeewick’ sounding call…don’t worry you can listen to both here.
The tawny owl is chestnut brown in colour (although they do come in other colours across Europe) and as you can see from the picture, it is designed to blend in with its preferred woodland habitat, although as can be seen from the nesting at Leg ‘o’ Mutton they’re happy to nest in more open habitat. This may be due to a lack of suitable nest sites elsewhere or food availability.
The annual cycle of tawny owls can be seen below, although it’s worth noting that the breeding pair at Leg ’o’ Mutton appear to have nested earlier than the average this year.
The eggs are incubated as soon as the first one is laid, so this causes the young to hatch asynchronously (at different time). This is a survival mechanism in case there is little food, so they are not feeding several hungry mouths at once.
The main food for Tawny owls is wood mice and bank voles. However, given the urban nature of the nesting site it is expected that their diet may be more varied than this and can include small birds, amphibians, large insects and earthworms. There is also evidence that shows tawny owls will feed on bats, especially in urban areas where other food sources may be limited. Given that Leg ‘o’ Mutton and the towpath are popular bat foraging routes I would not be surprised to find that they make up a part of their diet!
Territory sizes have found to vary from 20ha up to over 100ha, (Leg ‘o’ Mutton is a touch over 8ha for reference) but this will depend on the availability of food. For the pair at Leg ‘o’ Mutton this may take in the rough grassy margins of the neighbouring school fields and potentially Dukes Meadow over the river. Further afield sources of food would be the Wetlands and Barnes Common.
Other latest sightings and hatching at the reservoir include the several Grey Heron (Ardea cinereal) young that are now getting quite sizeable, as seen in the picture below. Herons nest in colonies called heronries. This can be found in the large London Plane (Platanus x hispanica) here, along the side of the reservoir.
The Blue tits (Cyanistes caeruleus) can also be found feeding young in the boxes on the hybrid Black Poplars (Populus x canadensis) and listen out for the Reed Warbler (Acrocephalus scirpaceus), Reed Bunting (Emberiza schoeniclus)and Chiffchaff (Phylloscopus collybita).
Southern, H.N. and Lowe, V.P.W., 1968. The pattern of distribution of prey and predation in tawny owl territories. The Journal of Animal Ecology, pp.75-97.
Speakman, J.R., 1991. The impact of predation by birds on bat populations in the British Isles. Mammal Review, 21(3), pp.123-142.
Hardey, J., 2006. Raptors: a field guide to survey and monitoring. The Stationery Office.