Many bird species have been successfully introduced beyond their natural range, some becoming more abundant in their new environment than in their country of origin. In this study, bird density was measured at 2 study areas comprising a total of 48 recreational parks in northern England and Canterbury, New Zealand, for 10 focal species (native to the former, introduced to the latter). Site characteristics and presence of other bird species were also recorded and investigated as potential explanatory factors for differences in density between the 2 study areas. Common redpoll, common starling, European greenfinch and house sparrow had significantly higher densities at the New Zealand sites. Analysis using generalised linear models revealed a negative relationship between common starling density and proportion cover of trees and shrubs, and a positive relationship between common redpoll, common starling and European greenfinch densities and site species richness. However, since there were no significant differences in site characteristics or site species richness between study areas, these relationships could not account for higher densities at the New Zealand sites. There was an apparent negative relationship between densities of common starling and house sparrow and foraging guild diversity, suggesting that interspecific competition may contribute to differences in density between study areas. The proportion of variation explained by the models was relatively low, suggesting that there may have been missing variables that influenced species density. More detailed study of a wider range of variables is required to investigate this further.
Nocturnal surveys for collared petrel (Pterodroma brevipes) indicate significant variation in the number of birds reported by site, time of year, and survey method. Collared petrels were recorded at 3 new islands within Fiji in 2011. These records indicate that locating collared petrels requires focussed survey effort, although they do not definitively confirm breeding on the islands, for which ground-based searches would be required. When visiting sites where there has been no recent evidence of collared petrel breeding, surveys should be undertaken between February and April (at the start of the breeding season), should use an active method of survey comprising both light for attraction and playback and/or with ‘war whooping’, and should be repeated at a number of sites before concluding that an island holds no breeding birds.
Orange-fronted (Cyanoramphus malherbi) and yellow-crowned parakeets (C. auriceps) are sympatric congeners that are secondary cavity nesting species, with the former being critically endangered. Both currently inhabit anthropogenically-modified Nothofagus forest. We compared the characteristics of nest sites in both species and found the majority of nest site parameters (tree height, height of hole above ground, DBH, tree condition and aspect) were similar. However, orange-fronted parakeets selected nest cavities with a significantly narrower entrance, and when situated in red beech (Nothofagus fusca), nest entrances were significantly smaller in area than in yellow-crowned parakeets. As the male orange-fronted parakeet is smaller in body mass than the male yellow-crowned parakeet (only males feed nestlings when laying multiple clutches), the difference in nest hole size may simply indicate that they are capable of utilising smaller entrances. We also found that orange-fronted parakeets selected nest holes in standing dead trees more frequently and nest sites in silver beech (N. menziesii) less frequently than expected. While the lack of differences in nest site characteristics suggests some interspecific competition may be occurring between these species (i.e., they occasionally use the same nest holes), it is difficult to establish this experimentally and to determine whether these differences are artefacts of former niche separation in unmodified forest.
A 15,000 ha low-intensity stoat (Mustela erminea) trapping network was established in the Murchison Mountains in 2002, primarily to protect the last natural population of the critically endangered takahe (Porphyrio hochstetteri). We compared the productivity and survival of threatened southern brown kiwi or tokoeka (Apteryx australis) living in 3 valleys that were covered by this trapping network with those in a nearby valley that was left untreated. Chick survival to 6 months old was significantly higher in the trapped areas (37%) than in the untrapped area (19%). This doubling of chick survival was sufficient to change the rate of population growth, as derived from Leslie matrix analyses, from a projected decline of 1.6% per annum without management to a projected increase of 1.2% per annum with trapping.
I recorded the calling behaviours of shining cuckoos (Chrysococcyx lucidus) from 1992 – 2015 on Kawau Island. The 3 most common calls, the upward crescendo “whistling call,” the downward slur “call-note,” and the “call-note” with “chatter” notes, were given from the arrival of adults in late August-early September until early January. After January only the call-note was heard. The upward whistling calls averaged 9.5 notes per calling bout (se = 0.18, n = 721). There was no significant difference in the number of whistling notes given with or without following notes. Single call-notes from lone cuckoos or groups of birds were restricted to specific sites on ridges. Calling was infrequently heard during evening twilight, and not heard during darkness. There was an increase in the number of cuckoo detections after 2009, and this corresponded with the appearance of communal behaviour and calling.