Differences in body composition between urban and rural Mallards, Anas platyrhynchos

Anthropogenic feeding of wildlife provides a valuable opportunity for people to engage with animals, but such feeding has the potential to be detrimental to the species involved. Ducks are frequently fed at urban ponds globally, yet the health impacts of an urban lifestyle for birds are poorly documented. We studied urban and rural Mallards (Anas platyrhynchos) in the Manawatū-Whanganui region (New Zealand). Mallards are opportunistic omnivores that have a phenotypically flexible gastrointestinal system. As urban Mallards consume considerable amounts of low-fibre, high carbohydrate foods via anthropogenic feeding, we predicted that urban Mallards would have smaller gastrointestinal tract organs and higher fat levels than rural ducks. We compared gross body composition of Mallards in a modified environment with high levels of feeding by humans and in rural habitats. We also evaluated other health-associated aspects including fat deposit size, liver fat content and haemosiderin (liver iron deposit) levels. Contrary to predictions, urban birds had larger gizzards and caeca and were no fatter than rural birds; rural birds additionally had larger pectoralis major muscles. These differences are probably associated with broader ecological and behavioural factors than with the provision of anthropogenic food per se [in particular the presence of hard foods (acorns and nuts) for urban birds, and higher flight activity of rural birds]. Longer caeca in urban birds could, however, relate to immunity rather than microbial fermentation of cellulose. Overall, while the nature of the local environment does affect Mallard physiology, no detrimental effects of urban living were evident in this study.Publishe

Geolocator wetness data accurately detect periods of migratory flight in two species of shorebird

While the principal use of light-recording geolocators is to determine geographical locations of migratory birds, supplementary wetness data have been used to refine estimates of minimum flight duration, on the assumption that a wet logger indicates the bird is on the ground. We provide a test of this assumption, by comparing wetness values against directly observed migratory departures of logger-equipped Bar-tailed Godwits Limosa lapponica and Red Knots Calidris canutus from the Manawatu River Estuary, New Zealand. Loggers recorded wetness every 10 min (Biotrack MK4093 and MK5093) or every one or four hours (Migrate Technology C65K). We retrieved loggers from 41 godwits from 2008– 2014 and from seven Red Knots in 2013–2014 for which we had corresponding departure information; in total there were 51 departures of godwits and seven of knots that we could match to actual departure times (this included multiple years for some godwits). Overall, 10-min wetness data were very accurate for both godwits and knots (median estimated departure times were 14 min and one min later than true departure, respectively), as were the 60-min and 240-min loggers on godwits if corrected by the wet counts that are recorded within measurement intervals (medians of 16 min earlier and 8 min earlier, respectively). These longer-interval loggers were still reasonably accurate without this adjustment (medians of 37 min and 74 min later, respectively). There was substantial variation between individuals and logger types, with 10-min loggers going dry up to 148 min (godwit) or 55 min (knot) earlier than true departure, while the 60-min and 240-min loggers recorded wetness up to 142 min or 124 min later than true departure (or 195 min or 232 min later, if unadjusted). Some of this variation simply reflects the interval over which wetness is recorded, but bird behaviour and/or logger performance must play a role in some cases (e.g. the logger going dry before departure or remaining wet after departure). Given observed bird behaviour upon arrival after migration (feeding on wet tidal flats), the wetness recording of geolocators is likely to give an accurate estimate of migratory flight duration, at least for species that frequent wet, particularly marine, habitats

Winter habitat use of New Zealand falcons (Falco novaeseelandiae ferox) in an intensively managed pine plantation, central North Island, New Zealand

Copyright and source must be acknowledgedPublishe

Do body condition and plumage during fuelling predict northwards departure dates of Great Knots Calidris tenuirostris from north-west Australia?

It is often assumed that strong selection pressures give rise to trade-offs between body condition and time in long-distance migrating birds. Birds that are 'behind schedule' in fuel deposition or moult should delay departure, and this should result in a negative correlation between initial condition and departure date. We tested this hypothesis in the Great Knot Calidris tenuirostris migrating from north-west Australia to eastern Asia en route to Siberia. Great Knot gain mass and moult into breeding plumage before leaving northern Australia in late March and early April, and fly 5400-6000 km to eastern China and Korea. We radiotracked 27 individuals (17 males and ten females) to determine departure dates; 23 migrated and four remained in Australia. We characterized body condition at capture using body mass, predicted pectoral muscle mass (based on ultrasound estimates of the size of the pectoral muscles) and breeding plumage scores. Residual condition indices were uncorrelated, indicating that at the individual level, variation in one fuelling component was not strongly associated with variation in the other components. Birds that did not depart had lower residual body mass and breeding plumage indices than those that did migrate; these four birds may have been subadults. Neither sex, size nor the condition indices explained variation in departure date of migrants. Reasons for this are explored. Departure dates for northward migrating waders indicate that the migration window (span over which birds depart) decreases with proximity to the northern breeding grounds. We suggest that migration schedules become tighter as birds get nearer to the breeding grounds. Thus the lack of a relationship between condition and departure date in Great Knots may reflect the fact that the departure episode under study is the first one in sequence and is still 4-8 weeks before breeding

Tracing exoplanets through time with TESS

In the thirty years since the discovery of the first exoplanet, over 5000 verified exoplanets have been discovered, unveiling a rich array of different exoplanetary architectures. However, there are still many unanswered questions regarding the formation and evolution pathways which have led to the observed population. To understand these processes it is imperative to trace exoplanets across time, both over galactic and human timescales. This thesis presents work in both of these areas, using data from the Transiting Exoplanet Survey Satellite (TESS). The bulk of this thesis focuses on the challenge of discovering new young exoplanets (age <1 Gyr) and understanding the variability of their potential host stars. This begins with building an extended population of young stars around which to search for exoplanets, illustrating the kinematic power of the recently launched Gaia satellite and resulting in a target list of over three million young stars. A dedicated new young star detrending pipeline is then presented, which is in turn used to search for new young exoplanets in stellar associations within TESS sectors 1-5. Although no new exoplanets were found, the pipeline’s effectiveness is demonstrated by recovering the previously known young exoplanets DS Tuc Ab and AU Mic b, alongside all other 2 min Targets of Interest (TOIs) from the 30 min cadence data alone. The completed young exoplanet search highlighted the challenging diversity of young stellar variability. To understand this variability, Kohonen Self-Organising Maps are used for the first time on a dedicated sample of young stars observed in the first year of TESS’s primary mission, in order to sort light-curves by topology and look for distinct variability classes. This analysis forms the first step in the YOUNGSTER programme, aiming to use knowledge of young star variability to inform more targeted detrending in future young exoplanet searches. Finally, this thesis presents work on tracing exoplanets through time on human timescales, updating and improving the ephemerides for all previously known Kepler planets (22) and candidates (4) which were observed with sufficient signal to noise in TESS. It also explores any transit-timing variations seen for these objects, including intriguing results for HAT-P-7b, Kepler-411d, K00075.01 and K00076.01