Effects of habitat type and management on the abundance of skylarks in the breeding season

Effects of habitat type and management on the abundance of skylarks in the breeding season Summary 1. There is increasing evidence to link major declines in skylark populations in Britain to agricultural intensification. However, whether causal mechanisms identified through localized studies can be generalized to the national scale remains unknown. The abundance of breeding skylarks was determined by surveying singing males in over 600 randomly selected 1‐km squares throughout Britain, in which skylarks recorded were assigned to homogeneous habitat patches. A more intensive survey of skylarks was carried out on lowland farmland sites in England. Singing males were assigned to specific crop types, and data on crop height and field boundary features were recorded. 2. Skylark occupancy (presence/absence) and density where birds were present (i.e. omitting zero counts) were analysed in relation to habitat type, habitat diversity and time of year, using generalized linear modelling. 3. Set‐aside, moorland and winter cereals had high rates of skylark occupancy at the national scale. Set‐aside had consistently high rates of occupancy and high densities across the breeding season at different spatial scales. Apart from set‐aside, there was little difference in density between habitats in the early half (March to mid‐May) of the breeding season. In the later half of the breeding season (mid‐May to July), density declined significantly on winter cereals, which showed significantly lower density than a number of habitats at this time, including spring cereals, legumes and moorland. 4. Within lowland farmland, there were significant effects of crop height on skylark occupancy, with crops of greater than 30 cm in height being occupied at relatively low rates. Winter cereals reached this height significantly earlier in the breeding season than a number of other crops, including spring cereals and legumes. 5. Skylark density increased with increasing habitat diversity across the whole sample of 1‐km squares and in lowland 1‐km squares in England. However, within the lowland farmland plots in England, skylark density showed a significant decrease with increasing habitat diversity. These conflicting results suggest that crop type rather than habitat diversity per se is important. 6. The effects of vegetation height on skylark abundance support the hypothesis that increases in winter cereal, and simultaneous loss of spring cereal, have had an adverse effect on skylark populations by reducing the number of breeding attempts made per year. These results support findings from smaller scale studies showing the generality of these habitat effects at different spatial scales. The extent of the British skylark population associated with agricultural land suggests that sympathetic changes in farming practice are likely to provide the best mechanism for improving the status of this species. The inclusion of options, such as spring cereal or fallow land (an equivalent to set‐aside), in agri‐environment schemes is likely to benefit skylarks breeding on farmland by providing suitable nesting habitat throughout the breeding season. In addition, reductions in the intensity with which cereals are managed, such as reduced pesticide and fertilizer input under approaches such as precision farming, and the creation of sparser patches of cereal sward, are also likely to increase the suitability of winter cereals for nesting skylarks. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Journal of Applied Ecology Wiley

Effects of habitat type and management on the abundance of skylarks in the breeding season

Loading next page...
 
/lp/wiley/effects-of-habitat-type-and-management-on-the-abundance-of-skylarks-in-FiWsQMEP73
Publisher
Wiley
Copyright
Copyright © 1999 Wiley Subscription Services, Inc., A Wiley Company
ISSN
0021-8901
eISSN
1365-2664
D.O.I.
10.1046/j.1365-2664.1999.00453.x
Publisher site
See Article on Publisher Site

Abstract

Summary 1. There is increasing evidence to link major declines in skylark populations in Britain to agricultural intensification. However, whether causal mechanisms identified through localized studies can be generalized to the national scale remains unknown. The abundance of breeding skylarks was determined by surveying singing males in over 600 randomly selected 1‐km squares throughout Britain, in which skylarks recorded were assigned to homogeneous habitat patches. A more intensive survey of skylarks was carried out on lowland farmland sites in England. Singing males were assigned to specific crop types, and data on crop height and field boundary features were recorded. 2. Skylark occupancy (presence/absence) and density where birds were present (i.e. omitting zero counts) were analysed in relation to habitat type, habitat diversity and time of year, using generalized linear modelling. 3. Set‐aside, moorland and winter cereals had high rates of skylark occupancy at the national scale. Set‐aside had consistently high rates of occupancy and high densities across the breeding season at different spatial scales. Apart from set‐aside, there was little difference in density between habitats in the early half (March to mid‐May) of the breeding season. In the later half of the breeding season (mid‐May to July), density declined significantly on winter cereals, which showed significantly lower density than a number of habitats at this time, including spring cereals, legumes and moorland. 4. Within lowland farmland, there were significant effects of crop height on skylark occupancy, with crops of greater than 30 cm in height being occupied at relatively low rates. Winter cereals reached this height significantly earlier in the breeding season than a number of other crops, including spring cereals and legumes. 5. Skylark density increased with increasing habitat diversity across the whole sample of 1‐km squares and in lowland 1‐km squares in England. However, within the lowland farmland plots in England, skylark density showed a significant decrease with increasing habitat diversity. These conflicting results suggest that crop type rather than habitat diversity per se is important. 6. The effects of vegetation height on skylark abundance support the hypothesis that increases in winter cereal, and simultaneous loss of spring cereal, have had an adverse effect on skylark populations by reducing the number of breeding attempts made per year. These results support findings from smaller scale studies showing the generality of these habitat effects at different spatial scales. The extent of the British skylark population associated with agricultural land suggests that sympathetic changes in farming practice are likely to provide the best mechanism for improving the status of this species. The inclusion of options, such as spring cereal or fallow land (an equivalent to set‐aside), in agri‐environment schemes is likely to benefit skylarks breeding on farmland by providing suitable nesting habitat throughout the breeding season. In addition, reductions in the intensity with which cereals are managed, such as reduced pesticide and fertilizer input under approaches such as precision farming, and the creation of sparser patches of cereal sward, are also likely to increase the suitability of winter cereals for nesting skylarks.

Journal

Journal of Applied EcologyWiley

Published: Dec 1, 1999

References

You’re reading a free preview. Subscribe to read the entire article.


DeepDyve is your
personal research library

It’s your single place to instantly
discover and read the research
that matters to you.

Enjoy affordable access to
over 18 million articles from more than
15,000 peer-reviewed journals.

All for just $49/month

Explore the DeepDyve Library

Search

Query the DeepDyve database, plus search all of PubMed and Google Scholar seamlessly

Organize

Save any article or search result from DeepDyve, PubMed, and Google Scholar... all in one place.

Access

Get unlimited, online access to over 18 million full-text articles from more than 15,000 scientific journals.

Your journals are on DeepDyve

Read from thousands of the leading scholarly journals from SpringerNature, Elsevier, Wiley-Blackwell, Oxford University Press and more.

All the latest content is available, no embargo periods.

See the journals in your area

DeepDyve

Freelancer

DeepDyve

Pro

Price

FREE

$49/month
$360/year

Save searches from
Google Scholar,
PubMed

Create folders to
organize your research

Export folders, citations

Read DeepDyve articles

Abstract access only

Unlimited access to over
18 million full-text articles

Print

20 pages / month

PDF Discount

20% off