The impact of raptors on the abundance of upland passerines and waders

Arjun Amar, Simon Thirgood, James Pearce-Higgins, Steve Redpath, Stephen Redpath

Research output: Contribution to journalArticle

9 Citations (Scopus)

Abstract

The issue of predator limitation of vertebrate prey populations is contentious, particularly when it involves species of economic or conservation value. In this paper, we examine the case of raptor predation on upland passerines and waders in Scotland. We analysed the abundance of five wader and passerine species on an upland sporting estate in southern Scotland during an eight-year period when hen harrier, peregrine and merlin numbers increased due to strict law enforcement. The abundance of meadow pipit and skylark declined significantly during this time. Golden plover also showed a declining trend, whereas curlew increased significantly and there was a near significant increase in lapwings. Contrasting the local population trends of these species with trends on nearby areas revealed higher rates of decline for meadow pipit and skylark at the site where raptors increased, but no differences in trends for any of the three wader species. There was a negative relationship between the number of breeding harriers and meadow pipit abundance the same year and between total annual raptor numbers and meadow pipit abundance. Predation rates of meadow pipit and skylark determined from observations at harrier nests suggested that predation in June was sufficient to remove up to 40% of the June meadow pipit population and up to 34% of the June skylark population. This 'quasi-natural' experiment suggests that harrier predation limited the abundance of their main prey, meadow pipit, and possibly the abundance of skylark. Thus, high densities of harriers may in theory reduce the abundance of the prey species which determine their breeding densities, potentially leading to lower harrier breeding densities in subsequent years. We found no evidence to suggest that raptor predation limited the populations of any of the three wader species. We infer that concerns over the impact of natural densities of hen harriers on vulnerable upland waders are unjustified.
Original languageEnglish
Pages (from-to)1143-1152
Number of pages10
JournalOikos
Volume117
Issue number8
DOIs
Publication statusPublished - Aug 2008

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raptor
passerine
birds of prey
meadow
highlands
predation
wader
breeding
Scotland
hens
law enforcement
Anthus pratensis
nest
vertebrate
vertebrates
nests
predator
predators
economics
trend

Keywords

  • Harrier circus cyaneus
  • Kestrels falco tinnunculus
  • red grouse
  • hen harriers
  • bird populations
  • habitat loss
  • predation
  • moorland
  • conservation
  • declines

Cite this

The impact of raptors on the abundance of upland passerines and waders. / Amar, Arjun; Thirgood, Simon; Pearce-Higgins, James; Redpath, Steve; Redpath, Stephen.

In: Oikos, Vol. 117, No. 8, 08.2008, p. 1143-1152.

Research output: Contribution to journalArticle

Amar, A, Thirgood, S, Pearce-Higgins, J, Redpath, S & Redpath, S 2008, 'The impact of raptors on the abundance of upland passerines and waders', Oikos, vol. 117, no. 8, pp. 1143-1152. https://doi.org/10.1111/j.0030-1299.2008.16769.x
Amar, Arjun ; Thirgood, Simon ; Pearce-Higgins, James ; Redpath, Steve ; Redpath, Stephen. / The impact of raptors on the abundance of upland passerines and waders. In: Oikos. 2008 ; Vol. 117, No. 8. pp. 1143-1152.
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AB - The issue of predator limitation of vertebrate prey populations is contentious, particularly when it involves species of economic or conservation value. In this paper, we examine the case of raptor predation on upland passerines and waders in Scotland. We analysed the abundance of five wader and passerine species on an upland sporting estate in southern Scotland during an eight-year period when hen harrier, peregrine and merlin numbers increased due to strict law enforcement. The abundance of meadow pipit and skylark declined significantly during this time. Golden plover also showed a declining trend, whereas curlew increased significantly and there was a near significant increase in lapwings. Contrasting the local population trends of these species with trends on nearby areas revealed higher rates of decline for meadow pipit and skylark at the site where raptors increased, but no differences in trends for any of the three wader species. There was a negative relationship between the number of breeding harriers and meadow pipit abundance the same year and between total annual raptor numbers and meadow pipit abundance. Predation rates of meadow pipit and skylark determined from observations at harrier nests suggested that predation in June was sufficient to remove up to 40% of the June meadow pipit population and up to 34% of the June skylark population. This 'quasi-natural' experiment suggests that harrier predation limited the abundance of their main prey, meadow pipit, and possibly the abundance of skylark. Thus, high densities of harriers may in theory reduce the abundance of the prey species which determine their breeding densities, potentially leading to lower harrier breeding densities in subsequent years. We found no evidence to suggest that raptor predation limited the populations of any of the three wader species. We infer that concerns over the impact of natural densities of hen harriers on vulnerable upland waders are unjustified.

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KW - conservation

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