Behavioural flexibility predicts invasion success in birds introduced to New Zealand

A fundamental question in ecology is whether there are evolutionary characteristics of species that make some better than others at invading new communities. In birds, nesting habits, sexually selected traits, migration, clutch size and body mass have been suggested as important variables, but behavioural flexibility is another obvious trait that has received little attention. Behavioural flexibility allows animals to respond more rapidly to environmental changes and can therefore be advantageous when invading novel habitats. Behavioural flexibility is linked to relative brain size and, for foraging, has been operationalised as the number of innovations per taxon reported in the short note sections of ornithology journals. Here, we use data on avian species introduced to New Zealand and test the link between forebrain size, feeding innovation frequency and invasion success. Relative brain size was, as expected, a significant predictor of introduction success, after removing the effect of introduction effort. Species with relatively larger brains tended to be better invaders than species with smaller ones. Introduction effort, migratory strategy and mode of juvenile development were also significant in the models. Pair-wise comparisons of closely related species indicate that successful invaders also showed a higher frequency of foraging innovations in their region of origin. This study provides the first evidence in vertebrates of a general set of traits, behavioural flexibility, that can potentially favour invasion success.     

Differential effects of exotic predator-control on nest success of native and introduced birds in New Zealand

The introduction of mammalian predators has been detrimental to many native birds in New Zealand. One solution to this problem has been the creation of “mainland islands” in which exotic predators are systematically removed. Although mainland islands have been effective in increasing some native bird populations, few studies have measured the effect of predator-control on nest success nor what effect control measures have on sympatric populations of introduced birds. We measured the effect of predator-control on nest survival rates in both native and introduced passerines in a mainland island near Kaikoura, New Zealand. Nest survival was significantly higher in Waimangarara Bush (the site with experimental predator-control) than in Kowhai Bush (the site with no predator-control) and this pattern was found in both groups of birds. However, mammalian predator-control increased nest success of native species significantly more than nest success of introduced species. This suggests that native birds benefit disproportionately from control of introduced predators, most likely because they lack behavioural defences against mammalian predators that are present among the introduced birds.     

Response of introduced European birds in New Zealand to experimental brood parasitism

The loss of anti-parasite adaptations against the European cuckoo Cuculus canorus was studied in three European passerine species, song thrush Turdus philomelos , blackbird T. merula , and chaffinch Fringilla coelebs , introduced to New Zealand in the 19th century. Chaffinches in New Zealand ejected non-mimetic eggs at a rate similar to their source population in the United Kingdom, but both song thrushes and blackbirds in New Zealand rejected non-mimetic eggs at a higher rate than the United Kingdom. It is not clear if this difference reflects variation among hosts in their response to brood parasitism or if it is an artefact of subtle differences in the types of non-mimetic eggs tested. In contrast, all three introduced species showed little aggression to a taxidermic model of a European cuckoo presented at their nests. This differs from European populations of these species, where model cuckoos are typically attacked. Our results suggest that in the∼130 years since their release in New Zealand, introduced birds have lost recognition of the European cuckoo but not their ability to discriminate non-mimetic eggs. The differential loss of anti-parasite adaptations by introduced birds in New Zealand suggests that cyclical models of host/parasite co-evolution may need to take into account the differing rates at which different host adaptations are lost and gained.     

Prevalence of blood parasites in European passeriform birds

Variation in the prevalence of blood parasites among species of birds has been used to test hypotheses about the effects of sexual selection and parental investment on disease resistance, and how vector abundance influences infection. However, the factors causing this variation are still poorly understood. We assessed the statistical effects of biogeographic, plumage-related and life-history traits on the prevalence of the blood parasites Plasmodium, Haemoproteus, Leucocytozoon and Trypanosoma in European passerine birds. Most of the variation in parasite prevalence occurred at low taxonomic levels. Brighter male plumage and greater host body mass were associated with higher prevalence, explaining 32% of the total variation. Male plumage brightness remained a significant factor when we controlled for phylogenetic effects. These relationships were driven primarily by simuliid-transmitted parasites (Leucocytozoon, Trypanosoma), which were more frequent in species with northern distributions. Host species with greater maximum longevity and shorter nestling periods had higher prevalences of Plasmodium; however, the effect was not stable after controlling for phylogeny using pairwise contrasts. Coevolution between hosts and parasites appears to create temporal and spatial variation that disconnects haematozoan prevalence from evolutionarily conservative life-history traits while creating some positive associations with traits that are phylogenetically labile. Clearly, ecologists should be cautious in relating patterns of variation in haematozoan prevalence to particular host traits.     

The role of species traits in the establishment success of exotic birds

There is now abundant evidence that propagule pressure, a composite measure of the number of individuals released into the nonnative location that varies between introduction events, is the most consistent predictor of success in the establishment of exotic species. However, the reasons why we expect propagule pressure to be important – because larger propagules ameliorate the effects of demographic, environmental or genetic stochasticity, or of Allee effects – also predict an influence of species traits on success. Here, we use a quantitative meta-analytical approach to assess the effect of three categories of species-level traits in the successful establishment of nonnative bird species: traits relating to population growth rates, traits that predispose species to Allee effects, and traits that enable a species to cope with novel environments. Traits that predispose species to Allee effects tend to decrease introduction success, whereas traits that enable a species to cope with novel environments tend to increase success. The breadth of habitats a species uses has the strongest mean effect of all variables analysed here. Mean effects for traits relating to population growth rates conflict in sign: in general, success is greater for species with large body mass whereas clutch size is not consistently related to establishment success. These results suggest a likely influence of some species-level traits on exotic bird establishment success, especially traits that enable a species to cope with novel environments. We suggest that considering such traits in terms of the small-population paradigm from conservation biology may be a productive avenue for future research.     

New species ofIsospora (Apicomplexa: Eimeriidae) from passeriform birds of Hawaii

Three new species ofIsospora (Apicomplexa: Eimeriidae) are described from the faeces of passeriform birds of Hawaii.Isospora lyonensis n. sp. is described from the faeces ofLonchura punctulata (Passeriformes: Estrildidae) and has spherical-subspherical oocysts, 24×23 (21–27×21–26.5), with a thick, bi-layered wall c.1.5 thick. A micropyle and oocyst residuum are absent, but three or more polar granules are present. Oocysts ofI. mejiro n. sp. were found in the faeces ofZosterops japonicus (Passeriformes: Zosteropidae) and are spherical to subspherical, 28.5×27 (25–32×25–29.5), with a thick, bi-layered wall c.1.5 thick. A micropyle and oocyst residuum are absent, but a large polar granule is present.I. manoaensis n. sp. was also found inZ. japonicus and has spherical-subspherical oocysts, 28×26.5 (25.5–30.5×22.5–29), and a thick, bi-layered wall c.1.5 thick. A micropyle and oocyst residuum are absent, but a polar granule consisting of numerous splinter-like fragments is present. In addition to the above new species, oocysts ofI. brayi Levine, Van Riper & Van Riper, 1980 were also found inZ. japonicus.     

Predation by mustelids and rodents on the eggs and chicks of native and introduced birds in Kowhai Bush, New Zealand

Prior to human settlement the endemic New Zealand avifauna evolved in the absence of mammalian predators. Subsequently mustelids, rodents and feral cats have become established and frequently prey on birds and nests. It has been suggested that, because of their evolutionary history, the endemic birds are especially susceptible to such predators. In this paper predation by mustelids and rodents on the eggs and nestlings of eight species of native bird is compared with that on five species of introduced European passerine inhabiting the same lowland forest.
Final outcomes were known for 101 nests of native birds and 48 nests of introduced birds found during three breeding seasons. There was no significant difference between the two groups in frequency of predation. Native birds lost 70-1% of their nests to predators and introduced birds 64-6%. Most predations occurred during the egg stage. Clutch size did not influence frequency of predation, but brood size did for Fantails and introduced birds. Stoats and weasels were responsible for 77-9% of predations on native birds and 77-4% on introduced birds; corresponding percentages for rodents (principally ship rats) were 14-7% and 19-4%. Mustelids destroyed proportionately more nests with chicks than with eggs, whereas rodents did the reverse. Predation on both groups of birds was not influenced by their nesting habitat, the species of tree used for nesting, or the height and position of the nest. The vulnerability to introduced predators of native New Zealand birds is discussed in relation to the historical declines of many species, and also their life-history patterns.     

The conservation of critically endangered flightless birds in New Zealand

The current status of Kakapo Strigops habroptilus and Takahe Porphyrio mantelli is described along with recent developments in programmes for their conservation. Both species were (at different times) thought to be effectively extinct, and both have been temporarily reprieved by the discovery of new populations. Population declines have continued, with Kakapo now reduced to less than 50 individuals and Takahe to about 150. Kakapo are especially at risk; 87% of the remaining birds are over 14 years old and only 17 females are known. Research on relict populations of both species has identified predation and competition from introduced mammals as major threats. Both species have high rates of egg infertility and low survival of young. Increasingly intensive management of both Kakapo and Takahe over recent years has included translocation to predator-free island refuges, supplementary feeding to encourage breeding, clutch manipulation, captive rearing and predator control. All known Kakapo have now been transferred to three island refuges, where the overall rate of population decline has slowed and supplementary feeding has apparently encouraged more frequent breeding attempts. Takahe conservation has concentrated largely on attempts to increase the population in Fiordland, New Zealand, through clutch manipulation and release of captive-reared young, but birds have also been released on four islands, which now hold 19% of the total population. The relict Fiordland populations of both Kakapo and Takahe were confined to apparently suboptimal habitat. Both species have successfully adapted to novel environments and foods when translocated, and the populations which now exist present improved opportunities for intensive management using a range of conservation techniques to enhance productivity and survival. Recent population trends of Kakapo and Takahe are reconstructed, and the contribution of research to their conservation is reviewed.     

New records of cestodes of New Zealand birds

Abstract

Ten species of cestodes are reported from aquatic birds in New Zealand. All are new records for the country.     

Influence of blood parasites on the body mass of passeriform birds

Body masses of 3,739 birds representing immature and adult males and females of 15 species of passeriforms (both uninfected and infected with Haemoproteus spp. and Leucocytozoon spp.) were compared. There was some interaction among year, month and area of capture for several host species, but there was no discernible effect of either parasite genus on body mass. There were no effects due to high intensity parasitemia for eight host species examined. Either parasitism does not cause loss of body mass, or the techniques used were too insensitive to separate effects of parasitism from other natural causes.     

Patterns of success in passeriform bird introductions on Saint Helena

Ecologists have long attempted to predict the success of species that are introduced into foreign environments. Some have emphasized qualities intrinsic to the species themselves, whereas others have argued that extrinsic forces such as competition may be more important. We test some of the predictions made by both the extrinsic and intrinsic hypotheses using passeriform birds introduced onto the island of Saint Helena. We found direct evidence that extrinsic forces are more important predictors of successful invasion. Species introduced when fewer other species were present were more likely to be successful. In a direct test of the alternative hypothesis that intrinsic forces play a more prominent role in success or failure, we found a tendency for species which successfully established on Saint Helena to be also successful when introduced elsewhere. However, the vast majority of species unsuccessful at establishing on Saint Helena had probabilities of success outside Saint Helena of 50% or greater, making this result somewhat equivocal. Finally, we found no evidence to support the hypothesis that species that are successful early are those that are intrinsically superior invaders. These results are consistent with similar analyses of the introduced avian communities on Oahu, Tahiti, and Bermuda.     

The introduced slugs of New Zealand (Gastropoda: Pulmonata)

Abstract

Eleven species of slug introduced into the New Zealand fauna are discussed: Testacellidae - Testacella haliotidea Draparnaud, 1801 (T. vagans Hutton, 1882 n.syn.); Arionidae - Arion intermedius (Normand, 1852), A. hortensis Férussac, 1819 (A. incommodus Hutton, 1879 n.syn.); Milacidae - Milax gagates (Draparnaud, 1801), M. budapestensis (Hazay, 1881), M. sowerbyi (Férussac, 1823); Limacidae - Deroceras reticulatum (Müller, 1774) (Limax molestus Hutton, 1879 n.syn.), D. panormitanum (Lessona & Pollonera, 1882), Limax maximus Linnaeus, 1758, Lehmannia flava (Linnaeus, 1758), L. nyctelia (Bourguignet, 1861). Of these, T. haliotidea, M. budapestensis, M. sowerbyi, D. panormitanum, and L. nyctelia are recorded from New Zealand for the first time. A key for the identification of these species is provided. Species thought to be doubtfully established are discussed, and a list is given of recent interceptions at New Zealand ports.     

Checklist of helminth parasites of birds in New Zealand

Abstract

A cross-referenced list is provided of 94 helminth taxa, at the generic or specific level, from 61 bird host species in the New Zealand subregion.