Yolanda van Heezik

Garden Size, Householder Knowledge, and Socio-Economic Status Influence Plant and Bird Diversity at the Scale of Individual Gardens

Domestic gardens collectively cover substantial areas within cities and play an important role in supporting urban biodiversity and ecosystem functioning. The extent of their contribution to urban biodiversity is ultimately determined by the attitudes, motivations, and practices of their owners. We identified variables characterizing individual householders and their properties that explained variation in perennial plant and avian species richness and plant diversity among 55 gardens in New Zealand. The size of the vegetated area was most important in explaining bird and plant diversity, independent of property size. Also important and positively associated with plant richness were socio-economic status and ability to discriminate between native and exotic species. Median housing age and neighborhood green space were less important. Contrary to expectations, better educated householders who demonstrated pro-environmental orientation (NEP) did not necessarily have gardens with greater plant diversity, however, people with higher NEP scores tended to have gardens with more structurally complex vegetation. Similar variables were important in explaining native and exotic species richness, but higher exotic plant diversity was associated with older people with smaller properties of lower value. Avian species richness increased primarily with vegetated area, but also the areas of beds and hedges. We demonstrate that although householder knowledge is an important determinant of garden biodiversity, vegetated area is most important. Promoting urban garden biodiversity requires that larger vegetated properties be supported and encouraged, and that planners should consider biodiversity when formulating policies concerning garden size, property size, and consents that may result in a progressive increase in the proportion of built over/paved areas.

Closing the Gap: Communicating to Change Gardening Practices in Support of Native Biodiversity in Urban Private Gardens

Private gardens collectively comprise the largest green space in most cities and the greatest potential for increasing the extent of wildlife-friendly and native-dominated habitat, improving the quality of ecosystem services, and providing opportunities for urban dwellers to reconnect with nature. Because attitudes and values driving landscape preferences in gardens are complex and often not conducive to biodiversity, and a gap exists between the possession of knowledge or values and the expression of pro-environmental behavior, facilitating change in gardening behavior is challenging. We attempted to improve knowledge and influence values, attitudes, and gardening behavior of 55 householders in favor of native biodiversity and environmentally friendly practices, through a two-way communication process, or interactive dialog, during a process of biodiversity documentation of their gardens. Informative feedback on their garden with a normative component was also provided. Despite being well educated and knowledgeable about common species at the start of the study, an increase in knowledge and shift in attitude was detected in 64% of householders: 40% reported a greater understanding of wildlife, and 26% made changes in their gardens, 13% to support native biodiversity. The normative component of our feedback information was of particular interest to 20% of householders. Because neighborhood norms influence gardening practices, changes adopted by a proportion of householders should be perpetuated across neighborhoods. The process of biodiversity assessment, dialog, and feedback was effective in improving knowledge of wildlife and native species, and stimulated a shift in attitude that resulted in native-friendly gardening practices. These changes were detected primarily through open self-report questions, rather than quantitative measures.

EFFECTS OF HATCHING ORDER, SIBLING ASYMMETRIES, AND NEST SITE ON SURVIVAL ANALYSIS OF JACKASS PENGUIN CHICKS

We used survival analysis to examine the fates of Jackass Penguin (Spheniscus demersus) chicks on Dassen Island, off the west coast of South Africa. There were two distinct phases of chick loss. The first, when chicks were 0-34 days old, involved losses primarily due to burrow collapse, exposure and drowning, and accidental death in the nest. This mortality was influenced strongly by nest-site characteristics. Overall reproductive success was lowest in open nests, intermediate in burrows, and highest in rock nests. The probability of chick death due to flooding was highest for burrows in shell/guano conglomerate, whereas the risk of burrow collapse was highest in sand. Burrows in high-density colonies had a greater likelihood of collapsing after heavy rain than burrows in low-density areas. The second phase occurred 42-90 days after hatch, when losses were almost entirely due to starvation. Comparisons of survival in control and experimental nests with varying degrees of sibling asymmetry indicate that it is the extent of hatching asynchrony that affects the ability of the smaller sibling to compete for food and that will produce sibling differences in the risk of starvation. Chicks in two-chick control nests starved at higher frequencies than chicks in less asynchronous experimental broods. Received 24 April 1990, accepted 17 December 1990. STUDIES of the breeding success of colonial seabirds may be hampered by the complexity with which many factors influence reproduc- tive success (Davis and McCaffrey 1986). In par- ticular, the inability to identify specific causes of chick mortality limits our knowledge of the factors that influence breeding failure. Recent studies of the Jackass Penguin (Sphe- niscus demersus) provided estimates of breeding success (Frost et al. 1976a, Cooper 1980, Randall and Randall 1981, Randall 1983, LaCock et al. 1987) without identifying specific causes of mortality or the timing of losses. No published study of the Jackass Penguin has considered either the timing of separate causes of chick mortality or the effect of sibling asymmetries on the probability of survival. We used survival analysis techniques (Davis and McCaffrey 1986) to (1) quantify the causes and timing of prefledging Jackass Penguin chick mortality; (2) investigate the effect of hatching order, chick number, and sibling size asym- metries on chick loss in natural asynchronous nests; (3) compare chick survival in natural asynchronous nests and experimental nests having different degrees of asynchrony; and (4) examine the influence of nest site on chick mor-

Seasonal, geographical, and age-related variations in the diet of the yellow-eyed penguin (Megadyptes antipodes)

Abstract A quantitative study of yellow-eyed penguin diet was carried out at two mainland breeding areas over a 2-year period, and at five other breeding areas over shorter time periods. Yellow-eyed penguins (Megadyptes antipodes) ate 26 prey species, with fish comprising 87% of the weight and 91% of the total number of prey items. Sprat occurred in the largest number of stomachs (70%) with red cod, opalfish, and squid in 49%, 42%, and 46%, respectively. Most prey items were <200 mm long. Prey were mainly pelagic species but also demersal species. The absence of inshore species in the diet and the distributions of prey species indicated that penguins travel away from the coast before beginning to feed, but remain over the continental shelf. Juvenile penguins ate more squid and less fish than adults, and weighed less. Differences in diet composition, body weights, and meal sizes were found between birds from different breeding areas, and between breeding seasons of contrasting reproductive success. Evidenc...

Movements of translocated captive-bred and released Critically Endangered kaki (black stilts) Himantopus novaezelandiae and the value of long-term post-release monitoring

Translocation outcomes for mobile species can be affected by post-release movement of individuals, yet few population reintroduction and supplementation projects con- sider propensity to move as a selection criterion when selecting individuals to release or sites for release. We investigate the influence of release age (juvenile or subadult), the size of the release group and the size of the wild population at the release site on movements of Critically Endangered kaki (black stilt) Himantopus novaezelandiae .O ver 460 subadult and juvenile kaki have been released during 12 years at nine sites in the Waitaki Basin, New Zealand, with the aim of supplementing specific sub-populations. Among the survivors that reached breeding age, 32% of released kaki ended up away from their release sites, i.e. away from the subpopulations they were intended to augment and 15% of these birds were in un- manageable areas where monitoring cannot take place. Kaki released as juveniles (2-3 months) made more long moves and moved further from the release site during 2 months post- release. The presence of conspecifics affected behaviour after release: released birds were more likely to remain closer to the release site when the size of the wild population at the release site was large, and kaki released in larger groups were more likely to make more longer moves. Despite initial differences in mobility, long-term monitoring revealed equal proportions of 2-year old survivors that had been released as juveniles and subadults returning and being observed consistently at rele- ase sites, emphasizing the value of long-term monitoring in informing release strategies for population restorations.

Seasonal changes in Houbara bustard Chlamydotis undulata macqueenii numbers in Harrat Al Harrah, Saudi Arabia: Implications for managing a remnant population

Abstract The Harrat al-Harrah reserve is currently the only area known in Saudi Arabia in which houbara bustards Chlamydotis undulata macqueenii may be found all year round, and in which breeding attempts still occur in most years. We examined the feasibility of obtaining estimates of houbara density in Harrat al-Harrah, and documented the pattern of seasonal changes in relative houbara abundance, relating this to abundance of crawling invertebrates and vegetation. Estimated densities of houbara ranged from 0·032 to 0·097/km 2 , which is low compared to estimates from other parts of the houbaras range. Variations in houbara numbers and flock sizes were not associated with concurrent changes in the availability of food resources. Seasonal changes in houbara abundance may be the result of movements by migrant houbara. Resource availability peaked in spring, when houbara numbers in the reserve were lowest, and when migrants were presumably taking advantage of similar resource peaks in their own breeding areas. These findings imply that encouragement of houbara populations in Harrat al-Harrah requires the protection or management of populations beyond the reserve, and probably even outside Saudi Arabia.

Cat-exclusion zones in rural and urban-fringe landscapes: how large would they have to be?

Context. The process of urban sprawl brings the human population and their domestic cats (Felis catus) in close contact with wildlife in areas that were previously remote, including reserves and conservation areas created to protect populations of vulnerable or threatened species. Various mitigation measures have been proposed, including devices designed to hinder cat hunting ability, desexing to reduce wandering and nuisance behaviours, containment at night or at all times and regulations governing cat ownership. Such regulations may aim to reduce cat densities by limiting the number of cats per household, or they may define zones around sensitive conservation areas where cat ownership is prohibited. Aims. The present study sought to establish the necessary size of cat-exclusion zones in rural and urban-fringe landscapes where vulnerable prey species may also reside. Methods. With GPS collars, we tracked 38 domestic cats at three sites (one rural, two urban fringe) where small reserves contained threatened lizard species. Key results. Home ranges (95% kernel density estimates) were considerably larger for cats at the rural site (0.3–69 ha) than at urban-fringe sites (0.35–19 ha at Kaitorete Spit and 0.2–9 ha at Otago Peninsula), and were larger at night than day. Resource selection ratios indicated avoidance of open areas with little cover, such as cultivated areas (farmland), tussock grassland and duneland, whereas sources of cover such as trees and buildings were preferred. Maximum distances moved and large variability between individual cats suggest buffers in rural landscapes would need to be at least 2.4 km wide, whereas those in urban-fringe habitat could be half as large. Conclusions. Despite significant home-range size differences exhibited by cats living in rural v. urban-fringe habitats, exclusion zones would need to be wide to account for considerable inter-cat variation in movement behaviour. Implications. The size of an effective cat-exclusion zone should represent the specific landscape, amount of residential development and substantial variability between individual cats.

Diets of yellow-eyed, Fiordland crested, and little blue penguins breeding sympatrically on Codfish Island, New Zealand

Diets of sympatrically breeding yellow-eyed (Megadyptes antipodes), fiordland crested (Eudyptes pachyrhynchus), and little blue penguins (Eudyptula minor) were examined over 1 week in late October ...

An Evaluation of the Accuracy and Performance of Lightweight GPS Collars in a Suburban Environment

The recent development of lightweight GPS collars has enabled medium-to-small sized animals to be tracked via GPS telemetry. Evaluation of the performance and accuracy of GPS collars is largely confined to devices designed for large animals for deployment in natural environments. This study aimed to assess the performance of lightweight GPS collars within a suburban environment, which may be different from natural environments in a way that is relevant to satellite signal acquisition. We assessed the effects of vegetation complexity, sky availability (percentage of clear sky not obstructed by natural or artificial features of the environment), proximity to buildings, and satellite geometry on fix success rate (FSR) and location error (LE) for lightweight GPS collars within a suburban environment. Sky availability had the largest affect on FSR, while LE was influenced by sky availability, vegetation complexity, and HDOP (Horizontal Dilution of Precision). Despite the complexity and modified nature of suburban areas, values for FSR ( = 90.6%) and LE ( = 30.1 m) obtained within the suburban environment are comparable to those from previous evaluations of GPS collars designed for larger animals and within less built-up environments. Due to fine-scale patchiness of habitat within urban environments, it is recommended that resource selection methods that are not reliant on buffer sizes be utilised for selection studies.

Population Characteristics and Morphometrics of Angulate Tortoises on Dassen Island, South Africa

Angulate tortoises (Chersina angulata) were probably introduced onto Dassen Island, South Africa, at the beginning of this century. Historical records indicate distance from the mainland appears to prevent emigration from, or immigration to, this island population. We estimated population size and density using a mark-recapture method, and determined sex ratio and population structure in 1978 and again in 1989. These figures were compared with published values for a mainland population. Population sizes and sex ratios did not differ significantly between 1978 and 1989: density was 31.2/ha and 34.2/ha, and sex ratios were 1:1.18 and 1:1.17 in favor of males, respectively. In both years the population showed a preponderance of adults. However, mean and maximum adult body size was greater in 1989. The island population was similar to the mainland population in terms of sex ratio and density, but differed in that there were proportionately more large males and females on the island. Factors that might cause an increase in size of island tortoises include predation on different sized tortoises by mainland compared with island predators. Reduced competition on the island and the potential effects of isolation may also affect body size. We suggest that the limits to the size of the island tortoise population will be primarily determined by numbers of breeding penguins and rabbits, whose activities remove vegetation used by tortoises for food and cover.