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The consequences of disrupted dispersal in fragmented red-cockaded woodpecker Picoides borealis populations.


Schiegg, K; Walters, J R; Priddy, J A (2002). The consequences of disrupted dispersal in fragmented red-cockaded woodpecker Picoides borealis populations. Journal of Animal Ecology, 71(4):710-721.

Abstract

1.
Habitat fragmentation may adversely affect animal populations through several mechanisms. However, little is known about how the impacts of some of these mechanisms are manifested in altered dynamics of wild populations.
2.
We used a spatially explicit individual-based simulation model to examine the potential effects of disrupted dispersal due to fragmentation on the population dynamics of the endangered, co-operatively breeding, red-cockaded woodpecker Picoides borealis.
3.
We simulated population dynamics as a function of population size and spatial aggregation of territories. Dispersal success (but not mortality or fecundity) was an emergent property of model runs. In the model all female and some male fledglings dispersed in straight lines in random directions, and the remaining males stayed on their natal territories as helpers and competed for breeding vacancies in their immediate neighbourhood.
4.
Population trend was tied to the higher dispersal success of both males and females in larger and less fragmented populations. Helpers were more successful than dispersing males. Male breeder recruitment depended entirely on helpers when populations were small (25 or 100 territories).
5.
Declining populations were characterized by high emigration rates and both failure and delay in female recruitment. The large numbers of unpaired males resulted in lowered reproductive output at the population level and in the loss of territories. Populations of 25 territories were stable when territories were highly aggregated, despite high emigration rates. These results closely match empirical observations.
6.
A number of co-operatively breeding species are endangered. The unusual dispersal behaviour of helpers may make such species sensitive to habitat fragmentation but also resilient to reductions in population size when territories are aggregated. Small populations of co-operative breeders may have considerable conservation value as a source of genetic diversity.

Abstract

1.
Habitat fragmentation may adversely affect animal populations through several mechanisms. However, little is known about how the impacts of some of these mechanisms are manifested in altered dynamics of wild populations.
2.
We used a spatially explicit individual-based simulation model to examine the potential effects of disrupted dispersal due to fragmentation on the population dynamics of the endangered, co-operatively breeding, red-cockaded woodpecker Picoides borealis.
3.
We simulated population dynamics as a function of population size and spatial aggregation of territories. Dispersal success (but not mortality or fecundity) was an emergent property of model runs. In the model all female and some male fledglings dispersed in straight lines in random directions, and the remaining males stayed on their natal territories as helpers and competed for breeding vacancies in their immediate neighbourhood.
4.
Population trend was tied to the higher dispersal success of both males and females in larger and less fragmented populations. Helpers were more successful than dispersing males. Male breeder recruitment depended entirely on helpers when populations were small (25 or 100 territories).
5.
Declining populations were characterized by high emigration rates and both failure and delay in female recruitment. The large numbers of unpaired males resulted in lowered reproductive output at the population level and in the loss of territories. Populations of 25 territories were stable when territories were highly aggregated, despite high emigration rates. These results closely match empirical observations.
6.
A number of co-operatively breeding species are endangered. The unusual dispersal behaviour of helpers may make such species sensitive to habitat fragmentation but also resilient to reductions in population size when territories are aggregated. Small populations of co-operative breeders may have considerable conservation value as a source of genetic diversity.

Citations

13 citations in Web of Science®
13 citations in Scopus®
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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:07 Faculty of Science > Institute of Zoology (former)
Dewey Decimal Classification:570 Life sciences; biology
590 Animals (Zoology)
Language:English
Date:2002
Deposited On:11 Feb 2008 12:14
Last Modified:05 Apr 2016 12:13
Publisher:Wiley-Blackwell
ISSN:0021-8790
Publisher DOI:https://doi.org/10.1046/j.1365-2656.2002.00637.x

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