Breeding Hen Harriers in Cumbria in 2002       Spring 2003

During 2002, there were two known Hen Harrier nesting attempts in the county. Both of these nesting attempts took place within a few hundred yards of each other, in the Geltsdale and Glendue Fells SSSI on land owned by the RSPB.

 Nest 1

Although an immature male was recorded throughout the winter, it was late February before another bird was sighted and a further two weeks before the number of sightings began to increase. Towards the end of March, a pair of harriers was regularly reported from the same location and it was here that harriers were first seen displaying on the 2nd April. Nest building was observed on the 12th April, followed by copulation on the 15th April and from this point onwards, this area was monitored on a daily basis.

This nest site was located along the reserve boundary, adjacent to a privately-owned grouse moor. It is a site where harriers regularly attempt to breed, but are rarely successful as a result of persecution. It takes six people working full-time to monitor a single nest and with the staff available, only one nest site could be monitored on a 24-hour basis. During these early stages of the breeding season, it was hoped that a pair of harriers might attempt to breed nearer the middle of the RSPB reserve. If this had happened, it would have been here that the effort required for nest monitoring would have been directed to give the greatest chances of success.

On Tuesday 7th May, the nest was checked and revealed the presence of six eggs (this had been done from a distance of several metres so as not to disturb the heather).

Observations of the nest area continued, but from 9th to 12th May a lack of food-passes indicated that the nest had failed. This was confirmed when the nest was checked for a second time on 14th May. All the eggs had gone and a trail was visible in the heather, leading directly to the nest. It is thought that the eggs were taken between the afternoons of 8th and 9th of May.

 Nest 2

By the stage in the season that the first nest had failed, it became apparent that this second pair would be the only other birds attempting to nest on the reserve in 2002. Despite the location, following the failure of the first nest, a 24-hour watch was set up involving RSPB staff, Hen Harrier Recovery Project Fieldworkers and a small number of volunteers. The location of the nest made monitoring extremely difficult, as the only safe place to watch the nest from RSPB land without causing disturbance was over 1km away. This was clearly too far to monitor the nest at night, so once the birds had gone to roost, field staff would carefully approach the nest and conceal themselves in the heather. Field staff would retreat just before dawn, which enabled the nest to be monitored 24 hours without causing any disturbance to the birds. The 24-hour watch commenced on 24th May and extended through to August.

The proximity of the second nest to the unsuccessful first nest made the task of documenting the breeding activity rather difficult. The birds (which were usually seen singly and at a distance) had to be identified individually, so it was possible to recognise to which pair they belonged.

Around the 7th May, the number of adult male sightings increased. However it was not until 9th May that the first confirmed sighting of a second male bird was made (identified by its wing-tags), which could account for the earlier increase in male activity. This second wing-tagged male began ‘sky-dancing’ on the 10th May and a couple of days later started to build a ‘cock’s nest’, around 300 metres away from the first nest. On the 14th May, the original male was sighted for the last time. On 12th and 13th May there were sightings of a female harrier that appeared to have lighter plumage than the first, although it was not known at this stage that the earlier nest had already failed. These two adult birds (both different individuals from the original pair) sky-danced together on 18th May and were seen copulating for a further ten days. Although they inspected the failed nest site, they eventually settled in the nest that the male had begun to build some days earlier.

Laying commenced on 22nd May and four eggs were present when the nest was visited on the 10th June. Incubation continued and the female was only seen to leave the nest each morning and during food passes, when the male brought in prey which the female consumed before returning to the nest. Mid-air food passes occurred until 25th June, around the time of first hatching, when the female was observed taking prey back to the nest to feed young.

Of the four eggs, only two hatched and these chicks were ringed and fitted with wing-tags and radio-transmitters in late July to monitor their dispersal. Wing-exercising had been observed from 24th July, but it was not until 4th August (male 41 days old, female 38) that both juveniles were observed making their first short flights. It is usual for males to fly at an earlier stage than females, but these juveniles were very well fed and possibly too heavy to fly. The nest continued to be used for prey deliveries and roosting during the next week. Both juveniles had bursts of flying activity around the immediate nest area and were often seen sparring. On 9th August the adult female was noted flying around the nest area with prey, the juveniles in hot pursuit. The juvenile female usually took control of kills and was seen to defend a kill against the juvenile male on more than one occasion. Both birds were flying over a greater distance but never out of sight of the prey delivery area.

Juvenile dispersal from Geltsdale

The juvenile birds from Geltsdale were roosting in rushes near the nest site and hunting over an increasingly large area. The number of prey-deliveries declined as the juveniles had to start hunting for themselves. Dispersal of the juveniles occurred from this location (male 24th August, female 26th August) 20 and 22 days after their initial flights.

From fledging to early September, the juvenile male could still be located in the vicinity of the nest site. By early September it had drifted to the south of Geltsdale, and was on the northern end of Moorhouse by the end of the month. In early October it was recorded further east around Plenmeller Moor, Whitfield and Asholme Commons SSSI although still frequenting moorland on the northern edge of Moorhouse/south of Geltsdale. By mid-October it was present in Upper Weardale and in early November this bird was recorded in Bowland.

The juvenile female deserted the nesting area earlier than the immature male, around the end of August. It was relocated in mid-September in the southeastern area of Moorhouse and Crossfell, and venturing around Cow Green & upper Teesdale. It was still present in these areas through to the end of October.

Juvenile dispersal from other English nest sites

Nestlings were fitted with radio-transmitters from breeding sites across England. These birds were monitored as they moved from their breeding grounds to their wintering quarters and a number of interesting observations were made.

It was expected that as birds became independent, post fledging, they were likely to make a single direct autumn migration, away from their natal area to a coastal wintering site. During early winter, multiple movements of birds were observed around the upland breeding areas. There was a mixing of immatures from the three discrete breeding sites in Northern England. Birds from Bowland moved to the Yorkshire Dales, birds from the Yorkshire Dales moved to Bowland and birds from Geltsdale also moved to Bowland. At one point, nearly all the immatures being tracked from the Dales and Bowland, were present within a relatively small area of moorland and may have been sharing a roost site.

The three breeding areas of Geltsdale, the Yorkshire Dales and Bowland are relatively isolated in terms of nesting habitat requirements: the deep heather to which harriers in England display such a preference. However, during winter the birds were frequently found hunting over rough grassland below the moorland edge and this type of winter feeding habitat is almost continuous between these sites. Initial results from the first year of the project suggested that some birds from these small isolated breeding populations could form a larger, more fluid, wintering population. Birds might move over areas of suitable habitat between their different breeding sites throughout the course of the winter. However, movements are likely to be affected by the weather and with only one season’s worth of radio-tracking data it is too early to draw any firm conclusions.

The English Nature Hen Harrier Recovery Project is entering its second year and we are requesting spring sightings. Hen Harriers that are reported can be monitored, and stand a far better chance of survival than those that are not. To forward any sightings please contact Richard Saunders tel: 01539 792800 or email: richard.saunders@english-nature.org.uk

Richard Saunders and Phil Curtis

English Nature Hen Harrier Recovery Project