Bird communities on habitat islands in England

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Abstract
Birds were recorded in 20 small woods (islands) and 8 control sites within larger woods in Oxfordshire. The number of species on islands was most highly correlated with area, but vegetation and isolation were also important. The number of species on control sites was significantly correlated only with the amount of vegetation above 5 m. Density of birds was correlated negatively with area and positively with density of the shrub layer on islands. Density in control sites was not correlated significantly with any of the variables studied. Four groups of birds were identified: (1) ubiquitous species, (2) resident species whose incidence increased with area, (3) locally distributed species, whose incidence was not obviously related to area and (4) transients. The second group may consist of species requiring large territories, the third group may include habitat specialists. Conservation of woodland birds in agricultural areas may be best achieved by a chosen collection of sites of various sizes rather than a single large site of similar total area. Both the number of species and density of birds could be maximized in this way.