Data from: Metapopulation dynamics of Roseate Terns: sources, sinks and implications for conservation management decisions
1. Habitat management to restore or create breeding sites may allow metapopulations to increase in size and reduce the risk of demographic stochasticity or disasters causing metapopulation extinction. However, if newly restored or created sites are of low quality, they may act as sinks that draw ind...
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Zusammenfassung: | 1. Habitat management to restore or create breeding sites may allow
metapopulations to increase in size and reduce the risk of demographic
stochasticity or disasters causing metapopulation extinction. However, if
newly restored or created sites are of low quality, they may act as sinks
that draw individuals away from better quality sites to the detriment of
metapopulation size. 2. Following intensive conservation effort, the
metapopulation of roseate tern (Sterna dougallii) in NW Europe is
recovering from a large crash in numbers, but most former colonies remain
unoccupied and hence are potential targets for restoration. To inform
conservation efforts, we studied the dynamics of this metapopulation with
a multistate integrated population model to assess each of the three main
colonies for important demographic contributors to population growth rate,
source/sink status and possible density dependence. 3. All three study
colonies are managed for roseate terns (and other tern species) in similar
ways but the demographic processes vary considerably between colonies. The
largest colony is a source involved in almost all dispersal, and its
growth is determined by survival rates and productivity. 4. Productivity
and juvenile apparent survival at the largest colony appear to be density
dependent. Although the mechanisms are unclear, this may provide an
increasing impetus for emigration of recruits to other colonies in the
future. 5. The smallest of the three colonies is a sink, relying on
immigration for its growth. Simulation models suggest the metapopulation
would be ~10 % larger in the absence of dispersal to the sink colony. 6.
This work indicates that, due to variable site quality, aims to enhance
both distribution and size of metapopulations may be mutually exclusive.
In this case, before future attempts to encourage recolonisation of former
sites, assessments of site suitability should be undertaken, focusing on
food availability and isolation from predators to maximise the likelihood
of attaining levels of productivity and survival that avoid creation of a
sink population to the detriment of the overall metapopulation size. |
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DOI: | 10.5061/dryad.6tv82c4 |