In Europe and North America waterfowl are major dispersers of aquatic and terrestrial plants, but in New Zealand their role has yet to be investigated. Mallards were introduced to New Zealand in the late 1800s, and today they are the most abundant and widespread waterfowl in the country. To assess seed dispersal, we radiomarked 284 female mallards from two study sites during the pre-breeding (June–August) and breeding (August–December) periods in 2014–2015, and examined movements that occurred within 24, 48 or 72 h when seed dispersal by endozoochory is considered likely. During June and July 2015, we collected 29 faecal samples from individual female mallards during radiomarking and 24 samples from mallard flocks. We recovered 69 intact seeds from the faecal samples and identified 12 plant taxa. Of the plant seeds identified and dispersed by mallards in this study, 40% were members of the Asteraceae family, nine plant species were alien to New Zealand, and the indigenous-status of three unidentified taxa could not be determined. Two taxa (and 9% of seeds) were germinated following gut passage: an unidentified Asteraceae and Solanum nigrum. During the pre-breeding and breeding periods, movement of females within 24 h averaged 394 m (SD = 706 m) and 222 m (SD = 605 m) respectively, with maximum distances of 3,970 m and 8,028 m. Maxima extended to 19,230 m within 48 h. Most plant species recorded are generally assumed to be self-dispersed or dispersed by water; mechanisms that provide a much lower maximum dispersal distance than mallards. The ability of mallards to disperse viable seeds up to 19 km within 48 h suggests they have an important and previously overlooked role as vectors for a variety of wetland or grassland plant species in New Zealand.

Abdominally implanted radiotransmitters have been widely used in studies of waterbird ecology; however, the longer handling times and invasiveness of surgical implantation raise important concerns about animal welfare and potential effects on data quality. Although it is difficult to assess effects of handling and marking wild animals by comparing them with unmarked controls, insights can often be obtained by evaluating variation in handling or marking techniques. Here, we used data from 243 female mallards (Anas platyrhynchos) and mallard–grey duck hybrids (A. platyrhynchos × A. superciliosa) equipped with fully encapsulated abdominally implanted radiotransmitters from 2 study sites in New Zealand during 2014–2015 to assess potential marking effects. We evaluated survival, dispersal, and reproductive effort (e.g., breeding propensity, nest initiation date, clutch size) in response to 3 different attributes of handling duration and procedures: 1) processing time, including presurgery banding, measurements, and blood sampling of unanaesthetized birds; 2) surgery time from initiation to cessation of anesthetic; and 3) total holding time from first capture until release. We found no evidence that female survival, dispersal probability, or reproductive effort were negatively affected by holding, processing, or surgery time and concluded that we collected reliable data without compromising animal welfare. Our results support previous research that techniques using fully encapsulated abdominal‐implant radiotransmitters are suitable to enable researchers to obtain reliable estimates of reproductive performance and survival. © 2017 The Wildlife Society.

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Stormwater catch basins form part of artificial drainage systems in urban areas and can provide larval habitat for mosquito vector species of West Nile virus (WNv), such as Culex pipiens Linnaeus (Diptera: Culicidae). We evaluated the impact of management techniques and targeted applications of larvicide on larval populations of this potential WNv mosquito vector species in catch basins from the Lower Mainland of Vancouver and on Vancouver Island of British Columbia, Canada. A mixed effects logistic regression model described the relationship between larval presence and larvicide treatment while controlling for other parameters. Parameter estimates showed that larvicide treatment reduced the odds of larvae presence by a factor of ,7.23. The model also revealed relationships between larval presence and water temperature and adjacent land use but larvicide treatment consistently reduced the presence of larvae regardless of these other factors. This knowledge can now be used to prioritise and target control efforts to most efficiently reduce WNv mosquito vector populations, and most effectively reduce the risk of WNv transmission to humans. A similar research strategy could be applied to emerging threats from other potential mosquito vectors of disease around the world, to help lower the incidence of mosquito-borne disease.Résumé-Les réseaux artificiels de drainage dans les zones urbaines comprennent des bassins de captage des eaux pluviales qui peuvent servir d'habitats pour les larves de moustiques vecteurs du virus du Nil occidental (WNv), tels que Culex pipiens Linnaeus (Diptera: Culicidae). Nous évaluons les impacts des techniques d'aménagement et des épandages ciblés de larvicide sur les populations de larves de cette espèce, un moustique vecteur potentiel du WNv, dans des bassins de captage dans les basses terres de la région de Vancouver et sur l'île de Vancouver en Colombie-Britannique, Canada. Un modèle de régression logistique à effets mixtes permet de décrire la relation entre la présence de larves et le traitement au larvicide, tout en tenant compte des autres variables. Les estimations des variables montrent que le traitement au larvicide réduit la probabilité de présence de larves par un facteur de l'ordre de 7,23. Le modèle montre aussi une relation entre la présence de larves, d'une part, et la température de l'eau et l'utilisation des terres adjacentes, d'autre part; cependant, le traitement au larvicide réduit toujours la présence des larves, quels que soient les autres facteurs. Ces informations peuvent servir à établir des priorités et fixer des cibles dans les programmes de lutte pour réduire le plus efficacement possible les populations de moustiques vecteurs du WNv et diminuer ainsi le risque de transmission du WNv aux humains. On pourrait utiliser une stratégie de recherche similaire pour étudier les nouvelles menaces que représentent d'autres moustiques vecteurs potentiels de maladies sur la planète afin de diminuer l'incidence des maladies transmises par les moustiques.

Investigating the reproductive ecology of naturalized species provides insights into the role of the source population's characteristics vs. post-release adaptation that influence the success of introduction programmes. Introduced and naturalized Mallards Anas platyrhynchos are widely established in New Zealand (NZ), but little is known regarding their reproductive ecology. We evaluated the nesting ecology of female Mallards at two study sites in NZ (Southland and Waikato) in 2014-15. We radiotagged 241 pre-breeding females with abdominal-implant transmitters and measured breeding incidence, nesting chronology and re-nesting propensity. We monitored 271 nests to evaluate nest survival, clutch and egg size, egg hatchability and partial clutch depredation. Breeding incidence averaged (mean AE se) 0.91 AE 0.03, clutch size averaged 9.9 AE 0.1 eggs, 94 AE 2% of eggs hatched in successful nests, partial depredation affected 6 AE 1% of eggs in clutches that were not fully destroyed by predators, and re-nesting propensity following failure of nests or broods was 0.50 AE 0.003. Nesting season (first nest initiated to last nest hatched) lasted 4.5 months and mean initiation date of first detected nest attempts was 28 August AE 3.3 days. Smaller females were less likely to nest, but older, larger or better condition females nested earlier, re-nested more often and laid larger clutches than did younger, smaller or poorer condition females. Younger females in Southland had higher nest survival; cumulative nest survival ranged from 0.25 AE 0.007 for adult females in Waikato to 0.50 AE 0.007 for yearling females in Southland. Compared with Mallards in their native range, the nesting season in NZ was longer, clutches and eggs were larger, and nest survival was generally greater. Different predators and climate, introgression with native heterospecifics and/or the sedentary nature of Mallards in NZ may have contributed to these differences.

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