Another reason why 10ha is too small

I don't recall this going through the first time.  Apologies if you've seen it before.
..............................................

Thought that this paper may be of interest (although I am not sure that you can do much about aggressive native species other than use this as evidence that further fragmentation of eucalypt forest habitat threatens populations of some bird species): 

Authors
 Piper SD.  Catterall CP.
Title
 A particular case and a general pattern: hyperaggressive behaviour by one
 species may mediate avifaunal decreases in fragmented Australian forests
Source
 Oikos. 101(3):602-614, 2003 Jun.
Abstract
 We quantitatively assessed edge effects associated with elevated abundance
 of a hyper aggressive bird species, the noisy miner Manorina
 melanocephala, in fragmented eucalypt forest adjoining developed land.
 Long-term data from Toohey Forest, subtropical Australia, show that noisy
 miner colonies intensively occupy a zone of 20 m from the forest edge,
 with frequent use occurring up to 100 m from the edge, but little beyond
 200 m. Within noisy miner colonies, the abundance and species richness of
 other birds were both about half those recorded at nearby transects which
 were outside the colonies' main activity area. Bird species smaller than
 noisy miners, which are also those with similar diets, were collectively
 20-25 times more abundant, and their species richness tenfold greater,
 outside miner colonies than within them, whereas larger species, which
 have less dietary overlap, did not differ. Exclusion of small
 insectivorous birds has been hypothesised to cause elevated insect
 herbivore density, but we found no difference between tree crown
 defoliation or dieback rates within versus outside miner colonies.
  
 Aggression by noisy miners can be viewed as a mechanism of interspecific
 competition, since miners have a relatively large body size for their diet
 and are hence able to exclude virtually all potential competitors at
 relatively little cost. We examine evidence indicating that reduced bird
 diversity in eucalypt forest fragments of eastern Australia is often
 simply the effect of noisy miner occupancy of edges, acting directly on
 the densities of other species through their aggressive behaviour. With an
 edge effect 200 m deep, a remnant 10 ha in size is likely to become
 entirely occupied by noisy miners, and this is a size threshold that has
 been commonly reported in association with area-standardised avian
 diversity reductions. Convergent patterns of species loss from small
 forest fragments in different continents are the result of different
 underlying ecological processes. [References: 49] 

Cheers

David Geering
Regent Honeyeater Recovery Coordinator
NSW National Parks & Wildlife Service
P.O. Box 2111
Dubbo  NSW  2830
Ph: 02 6883 5335 or Freecall 1800 621 056
Fax: 02 6884 9382





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