Grey and fawn variant plumages

Canada Geese in Yorkshire have extended their breeding range and habitat from traditional aquatic sites to include high-ground heather moorland. Many adults remain on the moors (with their goslings) to moult, and young reared here are an important source of unringed birds in the Yorkshire population and in the moulting flock on the Beauly Firth (Inverness-shire). Adaptations to moorland breeding are discussed; there is an absence of competition for nesting space such as characterises Canada Geese breeding in lowland aquatic sites.     

Radio‐transmitters do not affect seasonal mass change or annual survival of wintering Bicknell's Thrushes

ABSTRACT Studies of the effects of transmitters on passerines have provided mixed results, but many have revealed no negative impacts. Most such studies have been conducted during the breeding season and, as a result, little is known about the possible effects of transmitters on wintering birds. We examined the effects of transmitters on Bicknell's Thrushes (Catharus bicknelli) wintering in the Dominican Republic. We used long‐term mark‐recapture data to compare birds with radio‐transmitters (N= 5 years, 64 individuals) to birds banded, but not radio‐tagged (N= 10 years, 164 individuals). For a subset of birds in each category, we measured the change in mass between early‐winter and late‐winter and, for all birds, we calculated return rates and modeled annual survival by sex and age classes. Return rates of radio‐tagged (16%) and banded‐only individuals (17%) did not differ, and survival models including the effect of transmitter attachment were poorly supported. We also found no sex or age‐specific effects of transmitter attachment. Radio‐tagged and banded‐only birds did not differ either in the proportion of birds gaining mass during the winter or amount of mass gained. Our results indicate that attaching light‐weight transmitters (<5% of body mass) to wintering Bicknell's Thrushes did not adversely affect either body condition or annual survival.     

2. NOTES ON THE MASKED WEAVER

Radiotelemetry is an important tool used to aid the understanding and conservation of cryptic and rare birds. The two bird species of the family Picathartidae are little-known, secretive, forest-dwelling birds endemic to western and central Africa. In 2005, we conducted a radio-tracking trial of Grey-necked Picathartes Picathartes oreas in the Mbam Minkom Mountain Forest, southern Cameroon, using neck collar (two birds) and tail-mounted (four birds) transmitters to investigate the practicality of radio-tracking Picathartidae. Three birds with tail-mounted transmitters were successfully tracked with the fourth, though not relocated for radio tracking, resighted the following breeding season. Two of these were breeding birds that continued to provision young during radio tracking. One neck-collared bird was found dead three days after transmitter attachment and the other neither relocated nor resighted. As mortality in one bird was potentially caused by the neck collar transmitter we recommend tail-mounted transmitters in future radio-tracking studies of Picathartidae. Home ranges, shown using minimum convex polygon and kernel estimation methods, were generally small (<0.5 km²) and centred around breeding sites. A minimum of 60 fixes were found to be sufficient for home range estimation.     

Hematological stress indices reveal no effect of radio‐transmitters on wintering Hermit Thrushes

ABSTRACT Radio‐telemetry is often used to track birds, and several investigators have examined the possible effects of radio‐transmitters on birds. One approach to this question is to determine if transmitters induce physiological stress. Using hematological indicators of stress (heterophil‐lymphocyte [H/L] ratios), studies of captive birds have revealed no evidence that radio‐transmitters cause stress. However, studies in captivity may not reflect conditions faced by birds in the wild, especially during energetically demanding times, such as the overwintering period. We examined the possible effect of backpack‐style transmitters on overwintering Hermit Thrushes (Catharus guttatus) in South Carolina by examining H/L ratios from blood smears made before and after transmitter attachment. We captured and recaptured eight thrushes in an early winter period and 11 in a late winter period, and in both cases found that H/L ratios did not change after 1 mo of carrying transmitters. H/L ratios also did not differ significantly (in either trial) between thrushes with and without transmitters. Furthermore, thrushes that carried transmitters during both of our trials did not have higher final H/L ratios than those that carried transmitters during just one trial (the late winter). These results indicate that carrying backpack‐style transmitters for 1 mo did not induce stress in overwintering Hermit Thrushes. These results are consistent with studies of captive birds, and provide support for the continued use of backpack radio‐transmitters in this species, as long as weight recommendations are met.     

Non-permanent radiotelemetry leg harness for small birds

I developed a modified leg harness for mounting radiotelemetry transmitters to small birds, which includes a weak link that allows telemetry equipment to be shed. Over 4 years, I mounted 62 transmitters on 49 Tuamotu kingfishers (Todiramphus gambieri) using weak-link harnesses. Kingfishers retained 86% of transmitters for the duration of monitoring periods (23–66 days) whereas 22 of 23 transmitters were shed from birds resighted after 6–15 months. Apparent mortality was no higher for radio-marked birds than for birds without transmitters. The weak-link harness is an improvement to existing transmitter attachment techniques and provides a useful, effective, and ethical means of studying bird movements. © 2011 The Wildlife Society.     

Environmental change and the cost of philopatry: an example in the lesser snow goose

The consequences of philopatric and dispersal behaviours under changing environmental conditions were examined using data from the colony of Lesser Snow Geese (Anser caerulescens caerulescens) breeding at La Pérouse Bay, Manitoba, Canada. In response to increased population size and decreased food abundance over time, increasing numbers of family groups have been dispersing from the traditional feeding areas. Goslings from dispersed broods were significantly heavier (7.3%), and had longer culmens (3.1%), head lengths (2.6%) and marginally longer tarsi (1.9%) on average than goslings that remained within La Pérouse Bay itself. These differences were consistent in each of 5 years. There was no evidence that the larger size of dispersed goslings was due to either a tendency for larger adults to disperse to alternative sites, or increased mortality of smaller goslings among dispersed broods. The most likely cause for the larger size of goslings from dispersed broods was the significantly greater per capita availability of the preferred salt-marsh forage species at non-traditional brood-rearing areas. The larger goslings in non-traditional feeding areas showed significantly higher firstyear survival, suggesting that the use of deteriorating traditional feeding areas may currently be maladaptive in this population.     

Resource partitioning in sympatric arctic-breeding geese: summer habitat use, spatial and dietary overlap of Barnacle and Pink-footed Geese in Svalbard

The spatial, habitat and dietary overlap of two breeding goose species was studied in Sassendalen, Svalbard, in summer 2003 based on abundance within 500 × 500‐m grid squares and faecal diet analyses during pre‐breeding, nesting and post‐hatching periods. More than half of all Pink‐footed Geese Anser brachyrhynchus occurred in the absence of Barnacle Geese Branta leucopsis during nesting and post‐hatching periods compared to c. 20% when concentrated by pre‐breeding snow cover. In contrast, only 5% of Barnacle Geese were observed in the absence of Pink‐footed Geese pre‐breeding, 15% during nesting, and 35% post‐hatching. Among six defined habitat types, Barnacle Geese resorted more to ‘upland’ habitats during pre‐breeding and nesting and to lowland lakes post‐hatching when compared to Pink‐footed Geese. Although Pink‐footed Geese showed less change in seasonal habitat preference, many shifted to the river valley bottom post‐hatching, giving access to open water (predator avoidance) and lush green vegetation (foraging for goslings). The smallest extent of distributional overlap between the two species occurred post‐hatching, but each species was also highly restricted by snow cover during pre‐nesting. The greatest extent of overlap in distribution and diet occurred during incubation, when large dietary variation between different breeding valleys reflected local food availability around nests (probably a result of nest‐site preference rather than food selection per se). Whether this means that increased interactions within and between the two goose species with future increases in local density are most likely to be manifest at this stage of the summer is impossible to determine without knowledge of available food resources and manipulative experiments. More detailed investigations of the effects of foraging by both species on plant structure, quality and community composition are necessary to predict likely outcomes of future changes in population densities of both species.     

Effect of radio transmitters on return rates of Swainson's Warblers

ABSTRACT.   Although radio telemetry can provide useful information, the possible negative effects of transmitters, including biased results and detrimental effects on the birds, must also be considered. Several investigators have examined the effects of transmitters on larger birds, but few have examined their possible long-term effects, as assessed by return rates, on small passerines. We examined the possible negative effects of transmitters on a small (15.5 g) passerine. We used glue to attach radio transmitters to 40 male Swainson's Warblers ( Limnothlypis swainsonii ) at two study sites in Arkansas in 2005 and 2006. To assess possible effects of transmitters on survival, we compared the following-year return rates of radio-tagged birds to birds that were captured and color banded, but did not receive transmitters. Least squared mean return rates for all birds ranged between 0.46 and 0.57. We found no significant difference in the following-year return rate of radio-tagged and nonradio-tagged birds. In addition, we found no significant differences in return rates between study sites or years, and no significant interactions between any combination of radio transmitter (radio tagged or not), site, and year. Our results indicate that attachment of transmitters did not affect return rates of male Swainson's Warblers and that the glue-on technique is a good option for short-term studies of small passerines.     

Nicarbazin OvoControl G Bait Reduces Hatchability of Eggs Laid by Resident Canada Geese in Oregon

Abstract: Expanding populations of resident Canada geese (Branta canadensis) are resulting in increased conflicts with humans. Nonlethal and humane means are needed for managing Canada goose flocks at a variety of sites, including golf courses, industrial parks, government sites, and city parks. Decreased egg production and hatching are side effects of nicarbazin, a veterinary drug used to treat coccidiosis in chickens. Capitalizing on these effects, we developed nicarbazin as a reproductive inhibitor for Canada geese and conducted a field efficacy study. We recruited study sites in 2002 and 2003. Following laboratory testing, we conducted a field efficacy trial of nicarbazin for reducing the hatchability of Canada goose eggs in spring 2004 in Oregon, USA. The study began in February 2004 at 10 sites in Oregon, with 2 control and 3 treated sites on each side of the Cascades. We fed bait daily to resident Canada geese for approximately 6 weeks. We located and monitored nests until hatching or ≥5 days beyond the expected hatching date to determine hatchability. We completed data collection in May 2004. Geese consumed 8,000 kg of bait, with 5,100 kg of OvoControl G® (Innolytics, LLC, Rancho Santa Fe, CA) 2,500-ppm nicarbazin bait consumed among 6 treated sites and 2,900 kg of untreated bait consumed among 4 control sites. We monitored 63 nests at treated sites and 46 nests at control sites to determine hatching success of eggs. There was a 62% reduction in the percentage of nests with 100% hatchability at treated sites as compared to controls. There was a 93% increase in the percentage of nests at treated sites with 0% hatchability as compared to nests with no eggs hatching at control sites. Hatchability from treated sites versus control sites was reduced 36% (F = 5.72, P = 0.0622). We submitted results from this study to support Environmental Protection Agency registration of nicarbazin as a reproductive inhibitor for use in Canada geese. We have shown that treatment of resident Canada geese with OvoControl G 2,500-ppm nicarbazin bait by licensed, trained applicators immediately prior to and during the breeding season can reduce hatchability of eggs laid by treated geese, thereby reducing recruitment of goslings into problem resident Canada goose populations.     

Radio‐transmitters have no impact on survival of pre‐fledged American Woodcocks

American Woodcocks (Scolopax minor) are a high priority species of conservation need across most of their breeding range due to long‐term population declines. Survival of juveniles may be key to understanding these population declines, but there have been few direct estimates of juvenile woodcock survival rates, and no recent assessment of the possible effect of radio‐tagging on juvenile survival. In 2011 and 2012, we radio‐tagged 73 juvenile American Woodcocks in west‐central Minnesota and compared survival rates of radio‐tagged (N = 58) and non‐radio‐tagged (N = 82) juveniles during the period from hatching to fledging. We compared survival rates of juveniles with known fates and used logistic‐exposure models to assess the potential impact of radio‐transmitters on survival. We evaluated variables related to juvenile survival including age, hatch date, maximum and minimum temperature, precipitation, and year to assess the possible effects of radio‐transmitters. The best‐supported model of survival rate of juvenile American Woodcocks included the interaction of age and year and a negative effect of precipitation (β = ?0.76, 85% CI: ?1.08 to ?0.43), but did not include a negative effect of transmitters. Our results suggest that radio‐transmitters did not impact survival of juvenile American Woodcocks and that transmitters are a reliable tool for studying survival of juvenile American Woodcocks, and perhaps other precocial shorebirds.     

Use of Implanted Radiotransmitters to Estimate Survival of Greater Sage-Grouse Chicks

ABSTRACT Reduced chick survival has been implicated in declines of greater sage-grouse (Centrocercus urophasianus) populations. Because monitoring survival of unmarked sage-grouse chicks is difficult, radiotelemetry may be an effective technique to estimate survival rates, identify causes of mortality, and collect ecological data. Previous studies have used subcutaneous implants to attach radiotransmitters to hatchlings of several species of birds with precocial young. Previous researchers who used subcutaneous implants in free-ranging populations removed chicks from the capture location and implanted transmitters at an alternate site. Because logistics precluded removing newly hatched greater sage-grouse chicks from the field, we evaluated a method for implanting transmitters at capture locations. We captured 288 chicks from 52 broods and monitored 286 radiomarked chicks daily for 28 days following capture during May and June 2001–2002. Two (>1%) chicks died during surgery and we did not radiomark them. At the end of the monitoring period, 26 chicks were alive and 212 were dead. Most (98%, 207/212) radiomarked chick mortality occurred < 21 days posthatch and predation (82%, 174/212) was the primary cause of death. Necropsies of 22 radiomarked chicks did not indicate inflammation or infection from implants, and they were not implicated in the death of any chicks. Fate of 48 chicks was unknown because of transmitter loss (n = 16), radio failure (n = 29), and brood mixing (n = 3). Overall, the 28-day chick survival rate was 0.220 (SE = 0.028). We found that mortalities related to the implant procedure and transmitter loss were similar to rates reported by previous researchers who removed chicks from capture sites and implanted transmitters at an alternate location. Subcutaneous implants may be a useful method for attaching transmitters to newly hatched sage-grouse chicks to estimate survival rates, identify causes of mortality, and collect ecological data.     

Seasonal variation in growth of greater snow goose goslings: the role of food supply

Even though growth rate is an important fitness component, it is still controversial to what extent parent birds adjust the timing of offspring hatch to natural variations in food supply to maximize offspring growth. We studied the role of food availability in explaining inter- and intra-seasonal variation of growth rate in goslings of greater snow geese over 5 years. The peak of hatching generally coincided with the peak of food availability. However, early-hatched goslings usually grew faster than birds hatched at the peak, which in␣turn grew faster than late-hatched goslings, although this phenomenon was not observed in all years. There was considerable variation in growth rate among the five years, the smallest goslings produced in the best year (1991) being larger than the largest goslings of the poorest year (1994). We developed three indices of food availability, based on the cumulative availability of plant biomass and nitrogen content during the growth period, and showed that the cumulative exposure to nitrogen biomass explained up to 43% of variation (intra- and inter-annual) in body size just before fledging. In years with good feeding conditions, early-hatched goslings had access to more nitrogen during their growing period than those hatching on or after the peak and they grew faster. In years of lower food availability, early-hatched goslings had no detectable advantage over peak- or late-hatched birds for access to protein-rich food and no seasonal decline in growth rate was observed. These results confirm the critical role of food supply in the seasonal variation of growth rate in Arctic-nesting geese. Received: 27 June 1997 / Accepted: 9 October 1997     

Factors affecting the responses of female Canada Geese to disturbance during incubation

During incubation, Canada Geese (Branta canadensis) and other waterfowl flush from their nests in response to the approach of potential predators and subsequently return to nests after the threat of predation has abated. Differences among individuals in their responses to such disturbance (e.g., how close a potential predator approaches before flushing) are thought to reflect variation in female age, the reproductive value of clutches, and nest site characteristics. From 26 April to 26 May 2010, we examined the possible effects of these factors on the behavior of female Canada Geese (B. c. interior) on Akimiski Island, Nunavut. We used humans as surrogate predators and flushing distance and return time after disturbance as response variables. The distance at which females flushed in response to approaching humans was best explained by the density of vegetation around nests, with females on better concealed nests flushing at closer distances. We also found a weak relationship between return time and clutch size, with females with larger clutches returning to nests sooner. The frequency of human visits did not affect either female flushing distance or return time. Female Canada Geese in our study appeared to minimize risk of their own injury or death (future reproductive potential) in escape decisions, whereas return times appeared to minimize the risk of nest predation (current reproductive investment).     

Serological and virological survey and resighting of marked wild geese in Germany

In order to investigate the potential role of arctic geese in the epidemiology, the spatial and temporal spread of selected avian diseases, in autumn 2002, a virological and serological survey designed as capture-mark-resighting study was conducted in one of the most important coastal resting sites for migratory waterfowl in Germany. Oropharyngeal, cloacal swabs and blood samples were collected from a total of 147 birds comprising of three different arctic geese species including White-fronted Goose (Anser albifrons), Tundra Bean Goose (Anser fabalis rossicus), Pink-footed Goose (Anser brachyrhynchus) as well as from 29 non-migratory Canada Geese (Branta canadensis). Altogether, six adeno-like viruses (ALV; 95% CI, 1.74?C9.92%) and two avian paramyxoviruses (APMV-4; 95% CI, 0.19?C5.53%) were isolated mainly from juvenile White-fronted Geese. In addition, four Canada Geese were infected with lentogenic APMV-1 (95% CI, 3.89?C31.66%) at the date of sampling. No avian influenza viruses, reo-like viruses could be isolated despite serological evidence. Likewise, no evidence of current or previous infection by West Nile virus was found. Of the 147 birds tagged in the following years, 137 birds were re-sighted between 2002 and 2008 accumulating to 1925 sightings. About 90% of all sightings were reported from the main wintering and resting sites in Germany and The Netherlands. Eight of the resighted geese were virus positive (ALV and APMV-4) at the time point of sampling in 2002.     

Modified method for external attachment of transmitters to birds using two subcutaneous anchors

ABSTRACT Of the transmitter attachment techniques for birds, the subcutaneous anchor provides a secure attachment that yields relatively few secondary effects. However, the use of subcutaneous anchors has been limited by transmitter size and retention time. Using a modified method of attachment that utilized two subcutaneous anchors, we deployed 69 GPS transmitters, plus 13 VHF transmitters that were similar in size and weight to GPS models, on Pacific Black Brant (Branta bernicla nigricans). Prior to our study, only harnesses were used for attaching GPS transmitters on birds, mainly because GPS transmitters are too large for other external attachment techniques and implantation in the body cavity attenuates the GPS signal. Thus, to increase the size capacity of anchor attachment and to avoid the well‐documented negative effects of harnesses on behavior and survival, we added a second anchor at the transmitter's posterior end. The double‐anchor attachment technique was quickly and easily accomplished in the field, requiring bird handling times of <10 min. Incidental recoveries of tagged Brant indicate a high degree of transmitter retention. Five recaptured birds (4–6 weeks after deployment) and eight killed by hunters (3–6 mo after deployment) retained their GPS transmitters. For studies involving the use of relatively large transmitters, the double‐anchor method appears to provide a viable alternative for external attachment.     

Transmitter Effects on Growth and Survival of Forster's Tern Chicks

Radio-telemetry is a commonly used scientific technique that allows researchers to collect detailed movement, habitat use, and survival data of animals; however, evidence indicates that using telemetry can affect behavior and survival. Using multiple breeding colonies and years, we investigated the effects of attached radio-transmitters on growth and survival of Forster's tern (Sterna forsteri) chicks in San Francisco Bay, California, USA, 2010–2011. We tested these potential effects at isolated islands that allowed for high re-capture rates (typically >85%) in radio-marked and banded-only chicks. Modeled Gompertz growth curves suggested that transmitters had a small negative effect on some of the asymptotic growth parameters of tern chicks; tarsus (−1.5 ± 0.7% [SE]), culmen (−1.7 ± 1.2%), and wing (−4.9 ± 2.0%) lengths were shorter for radio-marked chicks compared to banded-only chicks. In contrast, there was no difference in asymptotic mass between radio-marked chicks and banded-only chicks. Survival from hatching to fledging was lower for radio-marked chicks than banded-only chicks during 2010 (banded-only = 0.313 ± 0.162 vs. radio-marked = 0.250 ± 0.165) and 2011 (0.193 ± 0.030 vs. 0.123 ± 0.027). Most of the transmitter effect occurred within the first week after hatching, rather than in older chicks. Notably, the effect of transmitters on chick survival was primarily additive, indicating that the effect of transmitters on radio-marked chicks was not influenced by other ecological covariates. Given the effect radio-transmitters had on survival did not change across temporal or ecological gradients, transmitters can still be used to evaluate ecological factors affecting survival and timing of mortality and radio-marked birds can be used to make inferences to the general population. Published 2020. This article is a U.S. Government work and is in the public domain in the USA.     

Do radio collars influence mortality and reproduction? A case with ring-necked pheasants (<Emphasis Type="Italic">Phasianus colchicus</Emphasis>) in Central Italy

The effect of radio transmitters on bird survival and reproduction has been explored in the literature, and contradictory results were found. Using the Kaplan–Meier method, we estimated the mortality of female ring-necked pheasants (Phasianus colchicus) in relation to radio load (percentage of total body mass). Low-load birds showed a higher survival, particularly after 2–3 months from release, thus excluding short-term effects of handling and adjusting to packages. Reproductive success was higher for birds with low loads, but the effect was less clear. The results were not influenced by age or body mass. As a rule of thumb, using radio packages lighter than 1.5% of the body mass can be considered safe for pheasants, whereas loads above 2% may have adverse effects.     

Survival of Dusky Canada Goose Goslings in Relation to Weather and Annual Nest Success

Abstract The dusky Canada goose (Branta canadensis occidentalis) population has been in long-term decline, likely due to reduced breeding productivity, but gosling survival of this population had not been examined. We studied gosling survival in broods of radiomarked adult females on the western Copper River Delta, Alaska, USA, during 1997–1999 and 2001–2003. Survival estimates for dusky Canada goose goslings to 45 days (x̄ = 0.32) were below estimates from most previous studies of geese. Daily survival of goslings increased with age and decreased with date of hatch. Precipitation during the first 3 days post-hatch was negatively related to gosling survival and this effect increased with date. Annual estimates of gosling survival were positively correlated with annual estimates of nest success, suggesting overlap in factors affecting nest and gosling survival. Nest success probably also directly affected gosling survival, because survival decreased with hatch date and more broods hatched from renests during years with low nest success. Gosling survival appears to play an important role in limiting current productivity of this population. Management directed at increasing nest success would likely also improve gosling survival. We recommend additional research directed at examining sources of gosling mortality and the link between nest success and gosling survival.     

Habitat selection and survival of Common Goldeneye (Bucephala clangula) broods — preliminary results

Factors affecting habitat selection and survival of individual Common Goldeneye (Bucephala clangula) broods were studied. Females were marked with radio transmitters and coloured wing tags, and their movements and that of their broods were followed to investigate the pattern of lake use.Broods frequently left hatching lakes and moved varying distances and made overland travels to reach actual brood rearing lakes. Food was more abundant and pH lower in rearing lakes compared with hatching lakes. Rearing lakes also were smaller and more isolated than hatching lakes but did not differ with respect to the structure of shore vegetation.Mortality rate varied considerably between broods. However, total distance moved and the length of overland travel was not associated with increased duckling mortality. Neither was mortality associated with the size, isolation or vegetation structure of the rearing lakes.     

Staging site fidelity of Greenland White-fronted Geese Anser albifrons flavirostris in Iceland

Capsule Based upon resighting histories of marked individuals, a high level of site loyalty was found for Greenland White-fronted Geese staging in Icelandic stopover areas in spring and autumn.

Aims To determine levels of within- and between-season staging site fidelity, to assess whether offspring adopt the staging areas of their parents and to determine relationships between Icelandic staging areas and winter provenance of individuals.

Methods Sequential resighting histories and recoveries (2658 observations) of 415 different individually marked geese were analysed from the period 1986–99.

Results In spring, > 90% of goslings associated with parents and siblings and all goslings were subsequently seen <4 km from where they were first sighted with parents in spring. Ninety-six percent of all multiple within-spring resightings of 192 marked individuals were within 4 km of each other; three geese moved 88 km from the southern to the western staging areas. Four percent of the 45 marked geese seen in two consecutive springs and none of the 27 birds seen in consecutive autumns moved more than 4 km between years. By contrast, significantly more (12%) moved greater than 4 km in subsequent seasons between spring/autumn (n = 56) and autumn/spring (n = 49). All these individuals shifted to Hvanneyri Agricultural College in autumn, the only declared hunting-free area for Greenland White-fronted Geese. Based upon resighting histories and recoveries of shot birds, Scottish wintering birds were more likely to use southern staging areas, and Wexford (Ireland) wintering birds were generally more likely to be seen staging in the western lowlands in Iceland.

Conclusions Given the apparent cultural reinforcement of patterns of use of staging areas in Iceland, the high levels of site loyalty and the relatively limited exchange between southern and western staging areas, we argue for strategic refuge designation throughout both staging areas to protect the population.