However, the direct effects of yellow crazy ants on land birds may be detrimental.
At very high densities, ants might disrupt nesting or even kill young birds (as
recorded for seabirds; Feare 1998, 1999a, 1999b); such losses would be particularly
severe for a small founding population. In the longer term, if the current loss of
Pisonia continues, the island will be much less suitable habitat for those bird species
which feed by gleaning invertebrates from foliage. On Mahe´, the Anoplolepis
outbreak which followed initial invasion in the 1960s has reduced in intensity. The
ants appear a less serious problem than in the initial stages of the outbreak (Haines
et al. 1994), in part due to the control measures first implemented in the 1970s
(Haines and Haines 1979a, 1979b, 1979c) and continued until at least 1995.
However, in part it may reflect population ‘boom and bust’ following establishment,
also displayed on other Indian Ocean islands, Agalega (coralline) and Rodrigues
(volcanic; Lewis et al. 1976). On a short visit to Bird Island in 2001, ant numbers
appeared to have significantly reduced from the levels recorded in 2000, suggesting
that this population may also follow a ‘boom and bust’ model, but the ‘bust’ is
unlikely to come before major effects on the existing flora and fauna of the island
are observed.
However, the direct effects of yellow crazy ants on land birds may be detrimental.At very high densities, ants might disrupt nesting or even kill young birds (asrecorded for seabirds; Feare 1998, 1999a, 1999b); such losses would be particularlysevere for a small founding population. In the longer term, if the current loss ofPisonia continues, the island will be much less suitable habitat for those bird specieswhich feed by gleaning invertebrates from foliage. On Mahe´, the Anoplolepisoutbreak which followed initial invasion in the 1960s has reduced in intensity. Theants appear a less serious problem than in the initial stages of the outbreak (Haineset al. 1994), in part due to the control measures first implemented in the 1970s(Haines and Haines 1979a, 1979b, 1979c) and continued until at least 1995.However, in part it may reflect population ‘boom and bust’ following establishment,also displayed on other Indian Ocean islands, Agalega (coralline) and Rodrigues(volcanic; Lewis et al. 1976). On a short visit to Bird Island in 2001, ant numbersappeared to have significantly reduced from the levels recorded in 2000, suggestingthat this population may also follow a ‘boom and bust’ model, but the ‘bust’ isunlikely to come before major effects on the existing flora and fauna of the islandare observed.
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