Kestrel - 2012 research report

Kestrel numbers within the county have declined and are now considered to be at their lowest level since 1894. The reasons for the decline are discussed in detail. Much of the decline is attributable to loss of suitable breeding habitat due to changes in farming practices, but there are also other contributing factors. Productivity seems sufficient to maintain a viable breeding population, but many successful breeding sites become unoccupied in subsequent years. This indicates that either adult survival between breeding seasons is too low, or insufficient recruitment is taking place due to low survival of first winter birds following independence, or perhaps both. A likely cause of the low survival of first winters is again change in farming practices reducing the foraging quality of the arable landscape but this assumes that Pembrokeshire kestrels disperse to lowland arable areas to over winter in line with the national trend (Shrubb 1993), an assumption for which there are no data to help validate. Predation cannot be ruled out as a cause of poor over-winter or post-fledging survival, but during the breeding season it appears to be insignificant. Competition for nest sites may occur inland and the provision of artificial sites in some areas may help, but it is concluded that nest site competition in not a significant factor that is driving the population decline, and until other factors are understood and mitigated for, then the kestrel population will not increase significantly in response to provision of artificial nest sites.

Read the full report here

Paddy Jenks & Tansy Knight 

Kestrel - 2003-07

The number of tetrads in which Kestrels were recorded, all categories, decreased from 156 to 97 between the two atlas survey periods. This 38% decline is likely to be genuine; the Kestrel is an obvious bird and is unlikely to be overlooked. The decrease has also occurred across all three categories. Using the confirmed and probable figures combined, the estimate for the breeding Kestrel population in Pembrokeshire is 30 to 35 pairs. This figure is backed up by the results of a dedicated census in 2008 which returned 31 breeding territories. A decline has also been recognised across the UK, particularly so in the southwest, and this decrease has also been accompanied by a decrease in productivity with fewer chicks fledging per nesting attempt (BTO nest record scheme).

A study in Kielder Forest, Northumberland, showed that predation by Goshawks caused a severe decline in the breeding Kestrel population (S. Petty 2003). The reasons for the decline in Pembrokeshire's Kestrels are not known for certain but an investigation which began in 2008 showed early signs that predation of nesting adults was occurring and brood size for 10 nests was significantly lower than the national average. It is also suspected that competition for nest sites with the larger and dominant Peregrine is an issue, particularly at coastal cliff and inland quarry sites.

A nest box scheme in Pembrokeshire was initiated in 2007, in an attempt to alleviate potential nest site competition but it is too early at the time of writing to assess its effect on the Kestrel breeding population.  Given the widespread decline in the west of UK, it would seem that the Kestrel’s future is insecure in Pembrokeshire.

Paddy Jenks

 

Fieldwork 2003-07 (based on 490 tetrads)

Red = breeding confirmed = 21

Orange = breeding probable = 15

Yellow = breeding possible = 60

Total tetrads in which registered = 96 (19.6%)

Buzzard - 2003-07

The distribution of Buzzards recorded during the two atlas survey periods is almost identical and the number of registrations 398 (405) is also very similar. Estimating the number of breeding pairs of Buzzards is fraught with problems. Many of the birds which are seen displaying and even lining a nest are non-breeding birds and studies indicate that only 25% of the population actually breed. Also a pair may frequently line more than one nest.

In their prime habitat of fairly well-wooded undulating countryside they can reach densities of up to 0.88 pairs per km2 (Simms et al 2001). Much of the east of the county can be considered to be perfect habitat, but in the more open and exposed west, breeding density is likely to be lower. If an average density is assumed of two to three pairs per tetrad over 250 tetrads in the east and one pair per tetrad over 150 in the West, then a population range of 650 to 900 pairs breed within the county, a considerable increase from the 1984-88 estimate of 250.  Increases of this order have been recorded at a UK level but the Welsh population has remained stable since 1994 (BTO website).

Given that the range has remained unchanged between the two survey periods then at least some of this increase may be explained by variation in the methods used to make the estimate.

Paddy Jenks

 

Fieldwork 2003-07 (based on 490 tetrads)

Red = breeding confirmed = 124

Orange = breeding probable = 167

Yellow = breeding possible = 107

Total tetrads in which registered = 398 (81.2%)

Sparrowhawk - 2003-07

There has been a clear decrease (23%) in the total number of tetrads in which Sparrowhawks were recorded between the two atlas periods. There was, however, virtually no change in the combined total of confirmed and probable breeding categories with the decrease occurring only in the possible breeding category. It is also notable that despite an overall decrease there were still 74 tetrads where Sparrowhawks were recorded during the later atlas for which there were no records during the 1984-1988 fieldwork. This makes interpretation difficult. It is possible that due to their secretive nature (especially during the incubation period in May and June)  Sparrowhawks were under-recorded in both surveys.

At UK level Sparrowhawks have shown a long term increase, reaching a plateau in the early 1990’s since when they have stabilised. However, in Wales there are insufficient BBS records to obtain a reliable trend (BTO website 2009). In summary, it appears as if there may have been a decline in Pembrokeshire’s breeding Sparrowhawk population but it is difficult to be sure of its extent (if any). Perhaps targeted monitoring with better suited methods is at least worthy of consideration.

An accurate figure for the breeding population is not possible from any fieldwork carried out within the county, but assuming at least 2 pairs per tetrad in which it is recorded then a minimum of 400 pairs occur. The true figure is likely to be higher.

Paddy Jenks

Fieldwork 2003-07 (based on 490 tetrads)

Red = breeding confirmed = 23 

Orange = breeding probable = 48

Yellow = breeding possible = 125

Total tetrads in which registered = 196 (40%)

Goshawk - 2003-07

During the last breeding atlas, a single pair of goshawks bred in the county. Since then they have colonised, presumably from the increasing core population in our neighbouring counties. By 2007 there were between 12 and 15 pairs and they are likely to continue increasing in both number and range within the county, though perhaps always with a bias towards the better wooded east and north.

They can be very easily overlooked especially after their initial display period in February to April but they tend to be site faithful so the distribution and population estimate can be considered reliable.

Paddy Jenks

Fieldwork 2003-07 (based on 490 tetrads)

Breeding confirmed = 4

Breeding probable = 11

Breeding possible = 13

Total tetrads in which registered = 28 (5.7%)

Red Kite 2003-07

Red Kites became extinct as a breeding species in Pembrokeshire in the latter half of the 19th century following intense persecution. They were not recorded breeding during the last atlas survey period but they had been noted lingering in the county into the summer (Rees and Donovan, 1994). The first proven breeding attempt since then was in 2002 when a pair laid eggs near Boncath. This attempt failed but another pair fledged two chicks near the Gwaun Valley in 2003. Since then kites have gradually colonised the north-east of the county. By the end of the survey period in 2007 there were twelve pairs holding territory, at least nine of which built nests, and further expansion has been observed since then. The origins of the colonising birds are not proven but strongly suspected to be from both Carmarthenshire and Ceredigion. During 2008 two adult birds both which were known to have been born in Pembrokeshire built a nest in the north of the county.

Whilst intentional persecution of Kites is happily now a rare event, they are still susceptible to poisoning either illegally by indiscriminate baits set for foxes and corvids or accidentally from second and third generation rat poisoning. This was brought home when one of the first two nestlings to fledge in 2003 was picked up dead before leaving the vicinity of the nest site having died of rat poison.

Another Pembrokeshire-born individual became a road casualty as it stooped to pick up carrion near Welshpool, Powys, during its first winter.

However, despite these incidents, overall survival rate is high and the Red Kite is set to return as widespread and common sight in the county to be enjoyed by all.

Paddy Jenks 

Fieldwork 2003-07 (based on 490 tetrads)

Red = breeding confirmed 

Orange = breeding probable 

Yellow = breeding possible 

Tetrads in which registered = 43 (8.8%)