The Implications of Metalandscape Connectivity for Population Viabilityin Migratory Songbirds |
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| Authors: | Kimberly A With Gregory R Schrott Anthony W King |
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| Institution: | (1) Division of Biology, Kansas State University, 66506 Manhattan, KS, USA;(2) Environmental Sciences Division, Oak Ridge National Laboratory, 37831 Oak Ridge, TN, USA |
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| Abstract: | Landscape connectivity is considered important for species persistence, but linkages among landscape populations (metalandscape connectivity) may be necessary to ensure the long-term viability of some migratory songbirds at a broader regional scale. Because of regional
source-sink dynamics, these species can maintain steady populations within extensively fragmented landscapes (landscape sinks)
owing to high levels of immigration from source landscapes. We undertook a modeling study to identify the conditions under
which immigration, an index of metalandscape connectivity, could rescue declining populations of songbirds in heavily disturbed
landscapes. In general, low to moderate levels of immigration (m = 0–20%) were sufficient to rescue species with low edge-sensitivity in landscapes where<70% habitat had been destroyed.
At the other extreme, moderate to high levels of immigration (m = 11–40%) were usually required to rescue highly edge-sensitive species in these same landscapes. Very high levels of immigration
(m>40%) were required to rescue highly edge-sensitive species in extensively fragmented landscapes that had lost >50% habitat,
or when any landscape lost ≥50% habitat gradually over a period of 100 or more years (r = 0.5% habitat lost/year). Paradoxically higher levels of immigration were thus necessary to offset population declines when
habitat was lost gradually than when it was lost quickly, where population response lagged behind landscape change. This implies
that the importance of metalandscape connectivity for population viability may not be fully appreciated in landscapes undergoing
rapid rates of change. Natural immigration rates for migratory songbirds match the very high levels (>40%) we found necessary
to sustain populations in heavily disturbed landscapes, which underscores the importance of metalandscape connectivity for
the continued persistence of many migratory songbirds in the face of widespread habitat loss and fragmentation. |
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| Keywords: | Birds Demographic model Habitat loss and fragmentation Immigration Landscape dynamics Neutral landscape models Source-sink dynamics |
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