The effect of predator control on survival of pheasants released on lowland farmland

Key points

  • Pheasants are an abundant and economically important gamebird in the UK.
  • This study combined data from several studies of radio-tagged pheasants both before, during and after the shooting season, to understand their causes of death.
  • Shooting was the cause of death for nearly 35% of radio-tagged pheasants.
  • On average, 19% of pheasants were predated or scavenged before the shooting season, and a further 15% during it.
  • Sites with a high level of predator control during the breeding season experienced a lower rate of hen pheasant predation.
  • At all sites, foxes were the main predator.
  • Predation of adult pheasants is reduced by effective predator control at the end of the shooting season and when they are breeding.

Background

Pheasant in woodland (www.davidmasonimages.com)Originally from Asia, pheasants are now the most common gamebird in the UK. Approximately 30-40 million pheasants are released for shooting each year. Pheasants are economically important, and revenue from shooting has funded research into gamebird conservation.

On commercial pheasant shoots, 6-7-week-old pheasants (poults) are released into open-topped pens in summer. Located in woodland, these pens have tall, wire-mesh sides to deter predators such as foxes while the birds get used to nesting in trees. After around three weeks, the pheasants fly out of the pen into nearby farmland where they mature before the shooting season (1 October - 1 February).

Pheasants are vulnerable to predation by foxes in particular, as they primarily stay on the ground in woodlands and fields, apart from when roosting. Before and during the shooting season, gamekeepers carry out predator control around the release site. Some estates continue predator control in the spring and summer to increase the survival of remaining birds for the following shooting season.

In this study, the authors monitored radio-tagged pheasants to investigate the effect of predator control on survival.

What they did

Radio tracking pheasantsData used in this study was collected over the course of 25 years from several studies. Specifically, data was collected on adult pheasant predation before and during the shooting season, and hen pheasant predation during the spring breeding season, when shooting had finished.

Predation before and during the shooting season

This part of the study was carried out on six estates in southern England. Foxes on each estate were controlled around release pens in summer, with some night-time shooting of foxes throughout the year. Predator control effort was calculated as the area covered by a full-time gamekeeper.

Between 2001 and 2003, 480 radio tags were attached to ten-week-old poults on these six estates. Throughout autumn and the shooting season, the radio tag was used to find each pheasant. Dead pheasants were examined for cause of death. Pheasants that were buried, had no head, or had a chewed radio tag were classified as predated or scavenged by foxes. Pheasants with plucked feathers were classified as predated or scavenged by birds of prey.

The number of pheasants predated before and during the shooting season was recorded, as well as the number of pheasants shot. This data was correlated with gamekeeping activity as the measure of predator control.

Predation during the breeding season

Data from seven further sites, monitored over 20 years, were divided into two groups depending on level of predator control during the pheasant breeding season. Three sites had a higher level of predator control, including tunnel traps for small mammals, corvid traps for magpies and crows, and snares for foxes. Four sites had a lower level of predator control, mainly of foxes, during the shooting season only.

A total of 811 hen pheasants were radio-tagged and observed throughout the breeding season over the years. Dead pheasants were examined for cause of death as before. The nests of tagged hen pheasants were also monitored. Nests were considered failures if the eggs or chicks were predated, or if the hen pheasant was predated during the incubation period.  

Rates of hen predation and nest success were recorded and compared between different levels of predator control effort for both wild and released pheasants.

What they found

Predation before and during the shooting season

Shooting was the cause of death for 35% of radio-tagged birds released from the six sites.

On average, 19% of radio-tagged pheasants were predated or scavenged before the shooting season, which ranged from 9-42%. A further 15% were predated or scavenged during the shooting season, ranging from 14-18%. In most cases foxes were identified as the cause, with birds of prey only linked to four cases.

There was high variation between years and between sites, but there was no significant effect of predator control level.

On average, 17% of pheasants released survived until the end of the shooting season.

Predation during the breeding season

Across the seven sites, between 20% and 71% of hens that survived the shooting season were predated between March and July. Predation was thought to be mainly by foxes, causing approximately 95% of recorded predation deaths.

Sites with a low level of predator control had a summer predation rate of 59%. Sites with a high level of predator control had a summer predation rate of 30%.

Most hen pheasant predation was either before or after incubation. Over a third of nests monitored were successful. There were only 31 cases of predation on incubating hens causing nest failure; these were all by foxes.

What does this mean?

Fox with pheasant (www.davidmasonimages.com)Released pheasants are particularly vulnerable to predation probably due to a lack of parental influence in the hand-rearing process, as well as genetic factors. Pheasants also spend most of their time on the ground at the edge of woodland and farmland, which are the preferred habitat of foxes and corvids.

There was a significant loss of pheasants to predators, mostly foxes, before and during the shooting season, although there was high variation between sites. There was no overall effect of predator control effort on predation rates.

However, survival of released pheasants before and during the shooting season was highly variable and depends on factors other than predation. These could include timing of release and shooting, local predator abundance, pen management and disease.

During the breeding season, around half of the hen pheasants that survived the shooting season were predated on average. A high level of fox control resulted in higher than average survival rate (70%). Predator control in spring and early summer can increase breeding success by reducing hen pheasant predation and nest failures.

The average nest success of pheasants at the seven sites was 34%. Although this may seem low, it is broadly similar to other wild farmland and woodland ground-nesting birds, for example skylark, corn bunting and woodcock. With the challenges of predation and disease, for many species breeding is successful for relatively few individuals each year. At only a third of nests succeeding to raise a chick, pheasants may be especially vulnerable, but many other species also experience these pressures. High levels of fox, mustelid and corvid control reduced nest failure at some sites.

Overall, predation of adult pheasants is reduced by effective predator control after the shooting season, and when they are breeding.

Read the original abstract

Sage, R.B., Turner, C.V., Woodburn, M.I.A., Hoodless, A.N., Draycott, R.A.H. & Sotherton, N.W. (2018). Predation of released pheasants Phasianus colchicus on lowland farmland in the UK and the effect of predator control. European Journal of Wildlife Research, 64 (14): 1-8.

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