Goshawk Habitat

Goshawk Habitat

GOSHAWK

Levels of disturbance, persecution and food supply appear to be key as to whether a pair can occupy and successfully sustain a territory – the first two factors presumably being particularly decisive for Norfolk. Some successful nesting sites are surprisingly small, but critical to the continued occupation of these territories appears to be either that the birds are actively protected or that the level of disturbance is low. Similarly, in some instances, what would appear to be suitable habitat is unlikely to support breeding Goshawk as the woodland is too disturbed, or the level of illegal killing may be high. Goshawk nesting in smaller woods are more vulnerable, so those nesting in larger woods tend to be more successful. Similarly, state-owned forests generally offer a safer haven for Goshawk than woodland on private shooting estates.

Goshawk nesting ranges can be used over many years but alternative ranges for the same pair may be up to 2.5km apart. It’s recommended that all known nesting ranges are checked first and then the search widened around those apparently unoccupied until either an occupied range is found or the territories of adjacent pairs are reached. Nest site locations can be frequently changed and if survey effort is concentrated mainly on known areas, it may miss a new area, label a territory as absent or assign a new pair to a location when it’s merely the same pair in a different location using an alternate nest site. Similarly, if a pair seems to be absent from a previously occupied area, this could give a false impression of a decline unless all suitable nearby woodland is searched.

Habitat

Goshawks normally favour large blocks of mature forests, but have been found in smaller woods of no more than 20-50ha. Goshawks defend only the nesting area, which is generally less than 5ha in size. However, they can nest in woods smaller than 3ha but usually only where there is a lack of more extensive woodland nearby. Less wooded sites have been used once core forest areas are occupied. Nesting areas usually occur in woods with a high density of mature trees and well developed canopy cover, surrounded by more open woodland. Stands of trees near nesting sites can differ noticeably from the surrounding woodland, containing larger and more widely spaced trees but with a fairly sparse understorey.

Nest trees tend to be larger than the surrounding trees, with sufficiently sturdy branches to support the substantial nest. For example, a closely packed commercial forest with spindly side branches is likely to be unsuitable, but even a relatively small clump of mature conifers which are taller than the surrounding deciduous woodland could be adequate. This tendency towards more open stands leads to a preference for plantations in the later stages of their lifespan, which can put the nesting area at risk of being felled. Old, very open stands of woodland with no secondary canopy development are avoided, unless there are no alternatives.

Home range

Goshawks hunt over open areas and within woodland, occupying extensive home ranges which can overlap with neighbouring pairs and areas used by non-breeders. The same territory may be occupied for a number of years, although not necessarily by the same birds. Home range sizes and nest densities vary with the availability of suitable prey and woodland. There is considerable overlap in winter when Goshawk range more widely for food.

Radio tracking has revealed that kills made in open country tend to be within 100m of woodland rather than deep in open country. Nests of neighbouring pairs have been found only 750m apart where there is no line of sight and 1200m apart if there is a direct line of sight. In lowland Britain, adjacent nest sites have been recorded from 1km to 3.7km apart in woodland blocks, although as much as 6km apart in Sweden.

Nesting range

The nesting range includes the area(s) containing all the known nest sites for one pair (or nest clusters if they are spread over a wider area), only one of which will be active in any year. Although alternate nests can be within a few hundred yards, Goshawks may move up to 2.5km to an alternative nest site and some pairs can have up to four different nesting areas within their nesting range. In suitable habitat, nest sites are regularly spaced.

Nests from different years are often clustered in a small area and some nests can be used many times. A study in lowland Britain found that most pairs had only a few nests with re-use being common, with only a minority of pairs building new nests. In northern England, more pairs tend to build new nests but then don’t go on to use them.

Although most alternate nests are grouped within a forest stand or cluster of adjacent stands, a search radius of 1km is recommended to locate 95% of alternate nests used. If disturbance is a factor in limiting where Goshawks nest, then presumably alternate nests may be more widely scattered if the original nesting wood becomes unviable.

Nest sites

Nesting ‘site’ refers specifically to the characteristics of the trees forming and surrounding the nest tree. Nesting areas can be the whole of an isolated wood or a stand of trees that differs from the surrounding woodland. Nest sites often occupy high ground in relation to the surrounding countryside, with a good outlook. Goshawk avoid nesting in valley bottoms unless there is no alternative. Nest areas can be used for a considerable time if not disturbed.

The characteristics of the site are more important than the tree species, with accessibility, a dense canopy and stable support for a large nest being essential. Nest sites are usually placed in areas of mature trees and well developed canopy cover, but with few large branches below canopy level, and surrounded by relatively open woodland. Good open flight access is needed to the nesting area for courtship, feeding and roosting activities, and fledglings need an open area to practise their flying skills. In closed canopy conifer plantations, Goshawk tend to prefer sites near paths, wind-throw openings, clearings, tracks or rides or thinned areas. In more open woods, nesting can occur away from the edges. If nest areas are on slopes, a north and east facing aspect seems to be preferred. Goshawk avoid nesting in stands which are either too thin with no secondary canopy development or too dense. Shrub / ground cover is often sparse, unless there is no alternative.

Nesting trees

Conifers are used as nesting trees in preference to broad-leaved, but they have been recorded nesting in the latter. One study area recorded 40 nests in conifers as opposed to 10 in broad-leaved. Trees particularly favoured include larch (even individual larches within an oak woodland have been selected), and pine, spruce, fir, beech, oak and sycamore have also been used. Trees as low as 12m have been chosen but the average tree height is above 20m.

Nests are nearly always built in the dominant trees in the stand, which may not always be the largest tree. In two areas of Britain, nests occupied stands of trees between 2.4 and 3.8 metres apart in conifers, and 2.5 to 8m apart in mixed conifers and broad-leaved trees.

References:

Anon. Goshawk breeding habitat in lowland Britain.

Anon. Breeding biology of Goshawk in lowland Britain

Brown, R., Ferguson, J., Lawrence, M., Lees, D. Tracks and signs of the birds of Britain and Europe.

Cieslak, M., Bolestaw, D. Feathers: identification for bird conservation. Natura Publishing

Etheridge, B. et al Raptors: a field guide to survey and monitoring, second edition

Kenward, R.E. Winter Predation in lowland Britain.

Marquiss, M., Newton, I. The Goshawk in Britain

Penteriani, V., Goshawk nesting habitat in Europe and North America: a review.

Petty, S. Goshawk: their status, requirements and management, Forestry Commission Bulletin

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