Alien Birds Research Articles

Population Trends of Forest Birds at Hakalau Forest National Wildlife Refuge, Hawai'i

Abstract. The Hakalau Forest National Wildlife Refuge was established to protect native Hawaiian forest birds, particularly endangered species. Management for forest restoration on the refuge has consisted mainly of removing feral ungulates, controlling invasive alien plants, and reforesting former pastures. To assess effects of this habitat improvement for forest birds, we estimated density annually by distance sampling and examined population trends for native and alien passerines over the 21 years since the refuge was established. We examined long-term trends and recent short-term trajectories in three study areas: (1) reforested pastureland, (2) heavily grazed open forest that was recovering, and (3) lightly grazed closed forest that was relatively intact. Three species of native birds and two species of alien birds had colonized the reforested pasture and were increasing. In the open forest, densities of all eight native species were either stable or increasing. Long-term trends for alien birds were ...

Inventory of alien birds and mammals in the Wallis and Futuna Archipelago

In November 2007 and November 2008, we conducted a bird and mammal survey on Wallis and Futuna. We found two non-native bird species on Wallis: the Common Myna (Acridotheres tristis) and the Chestnut-breasted Munia (Lonchura castaneothorax), and one on Futuna: the Jungle Myna (Acridotheres fuscus). We also recorded Black Rats (Rattus rattus) on Futuna, a recent introduction to this island. The introduction of 3 bird species and Black Rats in the last decade denotes a lack of preventive measures and demonstrates that the issue of invasive species has not received sufficient priority.

Biotic homogenization and alien bird species along an urban gradient in South Africa

Similar to the process seen in invasion biology, urbanized environments lead to biotic homogenization with a few species, often alien, dominating the urban habitat. We investigated avian communities across an urban gradient in Pretoria (South Africa). We defined three urbanization zones: urban, suburban and semi-natural, based on land-cover. We conducted point counts of all species at each of 13 sites in these zones over a 4-month period. We found significantly more species in the semi-natural zone than the urban zone but abundance was significantly lower in semi-natural than urban. The increase in abundance was mainly as a result of alien species with the three most abundant species in the urban zone being all alien. Semi-natural contained fewer alien species than urban and significantly fewer than suburban. The Common Myna Acridotheres tristis was the only alien species that was observed in all three urbanization zones and was the second most abundant species in the suburban and urban zones. Our study supports the process of biotic homogenization, where an increase in alien species occurs in the urban compared to semi-natural zone. Although the suburban zone made an important contribution towards native bird abundance in a larger city environment, this environment was also an important environment for alien species, especially for the Common Myna.

The role of species traits and taxonomic patterns in alien bird impacts

ABSTRACTAim To test whether the distribution of alien bird impacts varies across bird families and regions of origin, and to investigate whether species traits associated with successful introductions can predict which species will have negative impacts in the new area of introduction.Location Europe and the Mediterranean Basin.Methods Combining historical information and published literature about negative economic, biological and human health impacts, we compared the distribution of impacts among bird families and native origins of bird species for three major types of impact (economic, biodiversity and human health). We examined the relationships between ecological, biological and reproductive characteristics of species and the severity of the impacts.Results The majority of alien species with reported impacts originated from the Afrotropical, Indo‐Malayan and Palaearctic biogeographical regions. The distribution of alien bird species in Europe with reported impacts shows a taxonomic bias and largely mirrors patterns of establishment. While most species had primarily either economic or biodiversity impacts, several species in the Anatidae, Corvidae, Passeridae, Phasianidae and Sturnidae families were associated with moderate to serious negative impacts on both economic resources and native biodiversity. After controlling for taxonomic effects, species with the greatest overall impacts were habitat generalists and multi‐brooded, while species with smaller bodies and the tendency to form large feeding or roosting flocks were linked with greater impacts on native biodiversity.Main conclusions This study presents the first synthesis of published impact data for alien birds and provides a broad‐scale perspective on factors that contribute to their impacts. The results show that accounting for both species traits and taxonomy improves our ability to predict the impacts of alien bird species. Because several species are currently in the early stages of establishment in Europe, there may be an opportunity to limit negative impacts with efforts that promote proactive strategies against species and families possessing the above characteristics.

Alien and native birds in South Africa: patterns, processes and conservation

The spatial distribution of alien species richness often correlates positively with native species richness, and reflects the role of human density and activity, and primary productivity and habitat heterogeneity, in facilitating the establishment and spread of alien species. Here, we investigate the relationship between the spatial distribution of alien bird species, human density, and anthropogenic and natural environmental conditions. Next, we examined the relationship between the spatial distribution of alien bird species and native bird species richness. We examined alien species richness as a response variable, using correlative analyses that take spatial autocorrelation into account. Further, each alien bird species was examined as a response variable, using logistic regression procedures based on binary presence–absence data. A combination of human density and natural habitat heterogeneity best explained the spatial distribution of alien species richness. This contrasts with the results for individual alien species and with previous studies on other non-native taxa showing the importance of primary productivity and anthropogenic habitat modification as explanatory variables. In general, native species richness is an important correlate of the spatial distribution of alien species richness and individual alien species, with alien species being more similar to common species than to rare species.

Highland Forest Habitat Preference by Endemic Hawai‘ian Honeycreepers: A Preliminary Assessment

This paper examines the use of degraded, “suburbanized”-type highland forests in east Hawai‘i (Hawai‘i Island) versus more pristine, protected forest found in Volcanoes National Park by two endemic honeycreeper species, the apapane ( Himatione sanguinea ) and the amakihi ( Hemignathus virens ). This research is important because east Hawai‘i is experiencing rapid and extensive forest clearance due to a boom in home construction that began five years ago and continues today. This forest clearance not only destroys or degrades forest ecosystems, but it also leads to the introduction of exotic, usually ornamental plant species where few existed previously. The habitat fragmentation that has resulted also appears to be creating edge/fragmented environments in which alien bird species thrive. If current development and deforestation trends continue, further increasing the impact of edge/fragmentation-related effects, breeding populations of the remaining once-common honeycreepers may be relegated to the few large protected areas in Hawai‘i such as Volcanoes National Park and other fragmented forest islands. If this occurs, these species will be much more susceptible to catastrophic population declines. It is critical, therefore, that public officials work to protect remaining stands of native forest through new zoning laws that recognize the importance and uniqueness of east Hawai‘i’s native forests and their wildlife inhabitants.

Alien birds may be last hope for Hawaiian plants

Alien birds may be last hope for Hawaiian plants

How do habitat variability and management regime shape the spatial heterogeneity of birds within a large Mediterranean urban park?

Large urban parks can support a diverse bird community. However, the effects of variability among habitats and of park management on bird assemblages are poorly understood. We studied bird communities within the Yarkon Park, Tel Aviv, the largest urban park in Israel. We examined species richness, abundance and community composition across 20 locations that differ in levels of park management to identify habitat variables responsible for variation in bird richness and composition. Of 91 recorded bird species, 13 were aliens (14%), 4 were urban exploiters (4%), 54 were urban adapters (60%) and 20 were migrants (22%). Management had a significant effect on native bird richness and bird community structure varied among areas with different management regimes. Species richness of all the above species’ groups was lowest in intensively managed areas. Areas with intermediate levels of management had higher or equal richness compared to unmanaged areas. The majority of urban exploiters were found at all locations within the park reaching their highest abundances in intensively managed areas. Species richness of alien birds did not vary across levels of management. Bird species richness was negatively associated with lawn cover and with distance from nearest water source and was positively associated with the number of woody plant species. We suggest that urban parks should be designed such that the heterogeneity of native vegetation is preserved, if we aim to maintain native bird species diversity and minimize urban exploiter and alien species. When lightly managed or unmanaged, urban parks can retain large remnants of sub-natural habitats and can serve as important contributors to the conservation of native biodiversity within a large urban metropolis.

Ritual Releasing of Wild Animals Threatens Island Ecology

IntroductionHuman beings have served as both accidental and deliber-ate dispersal agents of various species of fauna and flora formillennia, but, nonnative species of plants and animals arenow appearing in new areas at a greater rate than everbefore and often to the detriment of native species. Inseveral countries people also practice various types ofreligious and spiritual freeing of wild animals, althoughvery little is known of the extent of these practices and theirimpact on the natural environment. In this paper, we discusshow the ritual freeing of wildlife promotes an invasion ofnonnative species, that is threatening the fragile islandenvironment of Taiwan.The term alien species refers to a species transported orestablished outside its native range by the activities ofhumans, whether intentionally or not. This definition doesnot imply that human-mediated dispersal of species isinherently unnatural, but it recognizes that the rate at whichhumans are homogenizing the world’s diverse biota isoccurring at a scale previously absent in Earth’s evolution-ary history (Williamson, 1996). For example, it has beenestimated that the rate of new species establishment in theHawaiian Islands was approximately one new species every35,000 years prior to human arrival; it is now on the orderof 20–30 species/year, which is a million-fold rate increase.Under the Convention on Biological Diversity (2002),invasive alien species means an alien species whoseintroduction and/or spread threatens biological diversity. Itrefers to a species, subspecies, or lower taxon introducedoutside its natural past or present distribution; it includesany part—gametes, seeds, eggs, or propagules—of suchspecies that might survive and subsequently reproduce.These organisms are sometimes called exotic, nonnative ornonindigenous species.Materials and MethodsWe conducted a survey between 2 February and 28November 2004 to record sightings of alien bird speciesin Taiwan. We surveyed different habitats such as forest,agricultural areas, villages, towns, and cities. Directobservation using binoculars (Leica 10×40) was carriedout to record bird sightings after randomly searching thesurvey areas during mornings (06:30–10:30) and evenings(15:30 to 18:30) using roads, trails, and footpaths. We useda car in urban areas while forest areas were surveyed onfoot. After sighting an alien bird species, data on thenumber, group structure (if found in groups), age-class,breeding status, and behavioral activities were recordedusing all-occurrences sampling method (Lehner, 1996).Data on the religious sites, such as temples and their rolein providing services to devotees to release wildlife intoTaiwan’s wilderness areas were pooled from Environmentand Animal Society of Taiwan (2004).Results and DiscussionA Small Island Exposed to Invasive SpeciesNinety-three percent of the total population in Taiwan,adhere to one of the two major traditional religions:

Relationships between alien plants and an alien bird species on Reunion Island

Many studies have shown that plant or bird invasions can be facilitated by native species, but few have demonstrated the possibility of a positive interaction between introduced species. We analysed the relationships between four invasive alien fleshy-fruited plants, Clidemia hirta, Rubus alceifolius, Lantana camara, Schinus terebinthifolius, and an invasive alien bird, the red-whiskered bulbul Pycnonotus jocosus introduced to Reunion Island (Indian Ocean). We compared the distribution of food items in the bulbul diet according to seasons and to abundance classes of this bird. Pycnonotus jocosus is mostly frugivorous and frequently eats the main alien plants (more than 80% frequency of food items). Sites with alien species, such as Clidemia hirta, providing fruits throughout the year supported more birds than sites providing fruits, such as Schinus terebinthifolius, seasonally. The birds facilitated seed germination by removing the pulp of fruit: the final per cent germination (FG) of cleaned seeds was higher than those within the fruit for three of the four plant species and in some cases passage through birds significantly increased FG (Schinus terebinthifolius) or Coefficient of Velocity (CV) (Lantana camara).

Biodiversity loss caused by invasive alien vertebrates

The introduction of invasive alien vertebrates is a major cause of the loss of native biodiversity in many regions of the world. The threats posed by them are especially severe on oceanic islands and other isolated ecosystems, in which there are many examples of extinctions or declines of native species caused by alien vertebrates. Predatory mammals are the worst offenders, but mammalian herbivores can also cause biodiversity loss and may provide the prey base to support invasive predators. There are also some notorious examples of alien birds, reptiles and fish that threaten native biodiversity. The adverse effects of invasive alien vertebrates are illustrated by specific examples from New Zealand, including the multiple impacts of Australian brushtail possums (Trichosurus vulpecula). Invasive vertebrates can sometimes be eradicated in the early phases of establishment and can be removed from islands or other isolated areas. However, given the uncertainty about the effects of alien species, the best policy is to adopt the precautionary principle and avoid making introductions without prior rigorous assessment of the risks to native biodiversity.

Darwin's Naturalization Hypothesis Revisited

In The Origin of Species, Darwin (1859) drew attention to observations by Alphonse de Candolle (1855) that floras gain by naturalization far more species belonging to new genera than species belonging to native genera. Darwin (1859, p. 86) goes on to give a specific example: “In the last edition of Dr. Asa Gray’s ‘Manual of the Flora of the United States’ ... out of the 162 naturalised genera, no less than 100 genera are not there indigenous.” Darwin used these data to support his theory of intense competition between congeners, described only a few pages earlier: “As the species of the same genus usually have, though by no means invariably, much similarity in habits and constitution, and always in structure, the struggle will generally be more severe between them” (1859, p. 60). Darwin’s intriguing observations have recently attracted renewed interest, as comprehensive lists of naturalized plants have become available for various regions of the world. Two studies (Mack 1996; Rejmanek 1996, 1998) have concluded that naturalized floras provide some support for Darwin’s hypothesis, but only one of these studies used statistical tests. Analyses of additional floras are needed to test the generality of Darwin’s naturalization hypothesis. Mack (1996) tabulated data from six regional floras within the United States and noted that naturalized species more often belong to alien genera than native genera, with the curious exception of one region (New York). In addition to the possibility of strong competition between native and introduced congeners, Mack (1996) proposed that specialist native herbivores, or pathogens, may be

Conservation Implications of Introduced Game Birds in High‐Elevation Hawaiian Shrubland

The Ring‐necked Pheasant (Phasianus colchicus) and the Chukar (Alectoris chukar) are the dominant avifauna in high‐elevation shrubland (2070–3000 m) of Haleakala National Park, Maui, Hawaii. We studied the food habits, ecological niche, and effects of these alien game birds on the native biota in this Hawaiian ecosystem. Analyses of crop contents indicated that pheasant and Chukar consumed predominantly fruits of native, woody dicots (39% and 47% respectively) and leaves (29% and 24% respectively) and flower parts (12% and 17% respectively) of alien, herbaceous dicots. Both species generally selected food items according to their relative availability, although other factors influenced choice of certain items. Invertebrates were a minor component of the game‐bird diet, suggesting that their impact on native invertebrate populations is minimal. Pheasant and Chukar occupy, at least partially, an ecological niche once held by now‐extinct or rare birds, and they appear not to be significant competitors with the endangered Nene. The role of these alien birds in facilitating seed dispersal and germination of native plant species is beneficial in restoring degraded ecosystems.

Alien taxa in the North American shrub-steppe four decades after cessation of livestock grazing and cultivation agriculture

Because of its use as a nuclear materials production area, the 800-km 2 sagebrush steppe of the Columbia River Plain in Washington State has functioned as a quasi-natural area protected from livestock grazing and agricultural development since 1944. Alien vegetation and animals have invaded the eastern Washington region in the past century and are currently represented in the Columbia River Plain. Investigations were undertaken to evaluate the distribution of alien species, particularly vegetation, and their relationships to other flora and fauna in this region. Recently disturbed areas were dominated by the alien annuals Russian thistle Salsola kali, tumble mustard Sisymbrium altissimum, prickly lettuce Lactuca serriola, and bur ragweed Ambrosia acanthicarpa. Old-field habitats were composed almost entirely of the alien annual cheatgrass Bromus tectorum. Alien vegetation also comprised a portion of the flora in habitats that had not been disturbed or grazed by cattle in the past. Cheatgrass and spring whitlow-grass Draba verna were able to set seed in undisturbed habitats, whereas Russian thistle and tumble mustard seldom did. These two species continue as components of undisturbed habitat primarily through seed dispersal from disturbed sites. Old-field habitats support a depauperate fauna compared to undisturbed sagebrush steppe vegetation. Shrub-nesting birds such as the sage sparrow Amphispiza belli were absent from old fields, and even ground-nesting species were found in abnormally low densities. Old fields supported relatively few mammal species, in part as a result of poor food supplies. Alien birds, the rock dove Columba livia and the European starling Sturnus vulgaris, visited undisturbed habitat, but did not nest there. No alien mammals were found in undisturbed sagebrush steppe vegetation; the only alien mammals found in the area, the house mouse Mus musculus and Norway rat Rattus norvegicus, being limited to riparian areas and the vicinity of buildings. Alien taxa are likely to remain a component of any quasi-natural area in the sagebrush steppe ecoregion. Human disturbance need not be spatially extensive to maintain alien plants within undisturbed communities. Successional patterns after land disturbance produce conditions unfavorable for native fauna, but have not enhanced the distribution of alien fauna.

Modes of perceiving and processing information in birdsong (Agelaius phoeniceus, Molothrus ater, and Homo sapiens).

In a previous study I examined the abilities of red-winged blackbirds and brown-headed cowbirds trained with a go-right/go-left procedure to identify conspecific and alien song themes (Sinnott, 1980). Results showed that each bird species exhibited superior identification of conspecific final "trill" or "whistle" elements, relative to the alien species. The present study extends these results by examining human perception of these same song stimuli, by examining the effects of tutoring birds with alien final song elements, and by using latency analyses to investigate processing modes that are not apparent from analyses of percent-correct scores. Results suggest three different processing modes: First, humans attend primarily to the final song elements. Second, birds identifying alien songs attend primarily to the introductory elements and disregard information in the final elements. Third, birds identifying conspecific songs process both the initial and final elements, but their response latencies indicate that they direct their attention primarily to the initial elements and process the final elements without investing more time than do the alien birds that fixate on the initial elements. Conspecific special processing is discussed in relation to various psychophysical, ethological, and psycholinguistic frameworks. Human perception of birdsong is discussed in relation to backward recognition masking.

Bionomics and Sociology of Tancho, Grus japonensis

Territoriality of Tancho or the Japanese Crane, Grus japonensis was studied in Kushiro marshlands from March 1971 to June 1972. Two types of social patterns are recognized: The permanent territorial pattern and the segregation of breeding and wintering areas. The difference of these two social patterns seems to be correlated with availability of winter food supply. Daily life of a pair is confined within a territory. The territory involves three important places for: nesting, roosting and feeding. The daily home range markedly varies, in the period of early parental care, its minimum size being as small as 1/1600 of the largest one. But the territory remains almost constant through breeding season. The alternation of guarding chick and searching food may be most responsible for the reduction of daily home range. To raise their chicks in huge open and bioeconomically poor marshlands, the reduction of daily home range is advantageous for Tancho. The territory occupants exhibit territorial defense at the invasion of alien birds. The sequence of invasion and defense varies considerably according to age of invaders, season, time and weather conditions. Duetting decreases the chance of invasion and increases the withdrawal of invaders. Social units found in Tancho in the breeding seasons are classified as territorial pairs, families, non-territorial two associated yearlings, solitary yearlings and solitary adults.