Untagged Birds Research Articles

Visitation rate, but not foraging range, responds to brood size manipulation in an aerial insectivore

Life history theory predicts that increased investment in current offspring decreases future fecundity or survival. Avian parental investment decisions have been studied either via brood size manipulation or direct manipulation of parental energetic costs (also known as handicapping). However, we have limited experimental data on the potential interactive effects of these manipulations on parent behavior. Additionally, we know little about how these manipulations affect spatial foraging behavior away from the nest. We simultaneously manipulated brood size and parental costs (via added weight in the form of a GPS tag) in wild female barn swallows (Hirundo rustica). We measured multiple aspects of parent behavior at and away from the nest while controlling for measures of weather conditions. We found no significant interactive effects of manipulated brood size and parental costs. Both sexes increased their visitation rate with brood size, but nestlings in enlarged broods grew significantly less post-brood size manipulation than those in reduced broods. Foraging range area was highly variable among GPS-tagged females but was unaffected by brood size. As such, increased visitation rate in response to brood size may be more energetically costly for far-ranging females. GPS-tagged females did not alter their visitation rate relative to un-tagged birds, but their mates had higher visitation rates. This suggests that GPS tagging may affect some unmeasured aspect of female behavior, such as prey delivery. Our findings indicate that investigation of foraging tactics alongside visitation rate is critical to understanding parental investment and the benefits and costs of reproduction.Significance statementAvian parental investment decisions have been studied by either brood size manipulation or direct manipulation of parental costs, but rarely both simultaneously. We simultaneously manipulated brood size and parental costs (via addition of a GPS tag) in a wild avian system, allowing us to examine interactive effects of these manipulations. Additionally, studies of parental investment often examine behaviors at the nest, but measurements of parental care behavior away from the nest are rare. Our study is unique in that we measured multiple aspects of parental care, including spatial foraging behavior tracked with GPS tags. We found no interactive effects of manipulated brood size and parental costs on visitation rate or nestling growth, and spatial foraging behavior of females was individually variable. Documenting foraging tactics alongside visitation rate is critical to understanding parental investment because the same visitation rate might be more costly for far-ranging females.

Great tits do not compensate over time for a radio-tag-induced reduction in escape-flight performance.

The use of biologging and tracking devices is widespread in avian behavioral and ecological studies. Carrying these devices rarely has major behavioral or fitness effects in the wild, yet it may still impact animals in more subtle ways, such as during high power demanding escape maneuvers. Here, we tested whether or not great tits (Parus major) carrying a backpack radio‐tag changed their body mass or flight behavior over time to compensate for the detrimental effect of carrying a tag. We tested 18 great tits, randomly assigned to a control (untagged) or one of two different types of a radio‐tag as used in previous studies in the wild (0.9 g or 1.2 g; ~5% or ~6–7% of body mass, respectively), and determined their upward escape‐flight performance 1, 7, 14, and 28 days after tagging. In between experiments, birds were housed in large free‐flight aviaries. For each escape‐flight, we used high‐speed 3D videography to determine flight paths, escape‐flight speed, wingbeat frequency, and actuator disk loading (ratio between the bird weight and aerodynamic thrust production capacity). Tagged birds flew upward with lower escape‐flight speeds, caused by an increased actuator disk loading. During the 28‐day period, all groups slightly increased their body mass and their in‐flight wingbeat frequency. In addition, during this period, all groups of birds increased their escape‐flight speed, but tagged birds did so at a lower rate than untagged birds. This suggests that birds may increase their escape‐flight performance through skill learning; however, tagged birds still remained slower than controls. Our findings suggest that tagging a songbird can have a prolonged effect on the performance of rapid flight maneuvers. Given the absence of tag effects on reproduction and survival in most songbird radio‐tagging studies, tagged birds in the wild might adjust their risk‐taking behavior to avoid performing rapid flight maneuvers.

Strong effects of radio‐tags, social group and release date on survival of reintroduced grey partridges

AbstractAnimal reintroductions are important tools for conservation but often fail for reasons poorly understood. Biological and methodological factors can affect reintroduction success in complex manners. Investigating dispersal after release often relies on the use of biologging devices but individuals cope differently with these devices. They can detrimentally affect the performance of individuals depending on life‐history stage and may provide flawed conclusions, because inference drawn from tagged individuals cannot be readily generalized to non‐tagged individuals. Furthermore, environmental conditions during the release period or the expression of social behaviour such as the coordination of flocking behaviour can affect the outcome of reintroductions. In a reintroduction project involving 1385 grey partridges (Perdix perdix) released in 54 social groups (i.e. coveys), we investigated whether individual biweekly post‐release survival varied throughout different life‐history stages and was affected by radio‐tags of different weight (8 vs. 11 g), covey affiliation and release date. We conducted experiments in captivity to evaluate whether physiological stress, body condition and individual take‐off performance were affected by radio‐tags. During the first month after release survival was low in radio‐tagged and untagged birds. Throughout the second‐ and third‐month post‐release, negative effects of radio‐tags on survival were apparent. Four months after release, the survival of radio‐tagged and untagged birds converged. Consequently, the annual survival of untagged birds was more than five times higher than that of radio‐tagged birds. We did not find clear negative effects of radio‐tags on stress hormone levels but take‐off performance tended to be lower in tagged birds. Survival strongly decreased with later release date and differed between coveys. The use of radio‐tags can detrimentally affect individual survival and reintroduction success of grey partridges. The risk and benefits of radio‐tags should be balanced and releases in reintroductions should be conducted under the most favourable social and environmental conditions.

Short-term behavioural impact contrasts with long-term fitness consequences of biologging in a long-lived seabird

Biologging has emerged as one of the most powerful and widely used technologies in ethology and ecology, providing unprecedented insight into animal behaviour. However, attaching loggers to animals may alter their behaviour, leading to the collection of data that fails to represent natural activity accurately. This is of particular concern in free-ranging animals, where tagged individuals can rarely be monitored directly. One of the most commonly reported measures of impact is breeding success, but this ignores potential short-term alterations to individual behaviour. When collecting ecological or behavioural data, such changes can have important consequences for the inference of results. Here, we take a multifaceted approach to investigate whether tagging leads to short-term behavioural changes, and whether these are later reflected in breeding performance, in a pelagic seabird. We analyse a long-term dataset of tracking data from Manx shearwaters (Puffinus puffinus), comparing the effects of carrying no device, small geolocator (GLS) devices (0.6% body mass), large Global Positioning System (GPS) devices (4.2% body mass) and a combination of the two (4.8% body mass). Despite exhibiting normal breeding success in both the year of tagging and the following year, incubating birds carrying GPS devices altered their foraging behaviour compared to untagged birds. During their foraging trips, GPS-tagged birds doubled their time away from the nest, experienced reduced foraging gains (64% reduction in mass gained per day) and reduced flight time by 14%. These findings demonstrate that the perceived impacts of device deployment depends on the scale over which they are sought: long-term measures, such as breeding success, can obscure finer-scale behavioural change, potentially limiting the validity of using GPS to infer at-sea behaviour when answering behavioural or ecological questions.

Backpack-mounted satellite transmitters do not affect reproductive performance in a migratory bustard

Backpack-mounted satellite transmitters (PTTs) are used extensively in the study of avian habitat use and of the movements and demography of medium- to large-bodied species, but can affect individuals’ performance and fitness. Transparent assessment of potential transmitter effects is important for both ethical accountability and confidence in, or adjustment to, life history parameter estimates. We assessed the influence of transmitters on seven reproductive parameters in Asian houbara Chlamydotis macqueenii, comparing 114 nests of 38 females carrying PTTs to 184 nests of untagged birds (non-PTT) over seven breeding seasons (2012–2018) in Uzbekistan. There was no evidence of any influence of PTTs on: lay date (non-PTT x̅ = 91.7 Julian day ± 12.3 SD; PTT x̅ = 95.1 Julian day ± 15.7 SD); clutch size (non-PTT x̅= 3.30 ± 0.68 SD; PTT x̅ = 3.25 ± 0.65 SD); mean egg weight at laying (non-PTT x̅ = 66.1 g ± 5.4 SD; PTT x̅ = 66.4 g ± 5.4 SD); nest success (non-PTT x̅ = 57.08% ± 4.3 SE; PTT x̅ = 58.24% ± 4.5 SE for nests started 2 April); egg hatchability (non-PTT x̅ = 88.3% ± 2.2 SE; PTT x̅ = 88.3% ± 2.6 SE); or chick survival to fledging from broods that had at least one surviving chick (non-PTT x̅ = 63.4% ± 4.2 SE; PTT x̅ = 64.4% ± 4.7 SE). High nesting propensity (97.3% year−1 ± 1.9% SE) of tagged birds indicated minimal PTT effect on breeding probability. These findings show that harness-mounted transmitters can give unbiased measures of demographic parameters of this species, and are relevant to other large-bodied, cursorial, ground-nesting birds of open habitats, particularly other bustards.

An automated positioning system for monitoring chickens’ location: Effects of wearing a backpack on behaviour, leg health and production

Automated tracking of the location of individual chickens is becoming more common in behavioural research. This technology has several advantages including gathering large amounts of data and monitoring of individual animals as opposed to flocks. To ensure the quality of the research the transmitters or tags attached to the bird as part of the automated positioning system should not have any effect on bird behaviour, welfare and production. Tag-related effects may lead to unreliable results which cannot be extrapolated to untagged birds. Therefore, we tested the effects of wearing a backpack containing a tag as part of an ultra-wideband system for automated position monitoring. The chickens’ behaviour, leg health, cleanliness and body weight gain were studied. Sixty slow-growing broiler chickens (Sasso XL451) were housed in groups of 10 birds. Per pen, five birds were fitted with a 36-g tag (TAG) in a backpack from day 35–70 and the other five were identified using colour markings (CON). Behavioural observations from video recordings of TAG and CON chickens were performed twice daily (15-min periods) every other day. Birds were weighed on day 35 and 70, and on day 70 foot pad and hock dermatitis, gait, and cleanliness were scored. TAG birds walked less than CON birds in week 6, but this difference was absent from week 7 onwards. CON birds pecked more at TAG birds than other TAG birds did in week 6, probably due to the novelty of the tags, whereas the TAG birds could investigate their own tag instead of pecking at other birds’ tags. No significant differences were observed for scores for foot pad and hock dermatitis, gait and cleanliness scores or weight gain between TAG and CON birds. These results indicate that the backpacks with tags had only minor, non-persistent effects on slow-growing broiler chickens’ behaviour. The effects of colour-marking on behaviours observed in this study are likely to be small. The results indicate that the tags can be used for further studies in which these behaviours, welfare measures and production parameters play an important role.

The effects of leg-loop harnesses and geolocators on the diurnal activity patterns of Green Sandpipers Tringa ochropus in winter

ABSTRACTWe have measured the activity patterns of wintering Green Sandpipers before and after they were fitted with geolocators attached using leg loop harnesses and compared these with a control group of untagged birds. The geolocators and harnesses represented 1.4–1.6% of the body mass of the birds. Although the proportion of time the birds spent feeding increased over the course of the winter, we found no significant effect of tagging. Tagged birds spent significantly more time preening than untagged birds (6.3% overall compared with 4.6% for untagged birds) but the effect decreased with days after tagging. There was no evidence that this small increase in preening activity led to lower survival of the birds or changes in their migration timetable.

An experimental evaluation of the effects of geolocator design and attachment method on between-year survival on whinchatsSaxicola rubetra

Data from location logging tags have revolutionised our understanding of migration ecology, but methods of tagging that do not compromise survival need to be identified. We compared resighting rates for 156 geolocator-tagged and 316 colour ringed-only whinchats on their African wintering grounds after migration to and from eastern Europe in two separate years. We experimentally varied both light stalk length (0, 5 and 10 mm) and harness material (elastic or non-elastic nylon braid tied on, leg-loop ‘Rappole’ harnesses) in the second year using a reasonably balanced design (all tags in the first year used an elastic harness and 10 mm light stalk). Tags weighed 0.63 g (0.01 SE), representing 4.1% of average body mass. There was no overall significant reduction in between-year resighting rate (our proxy for survival) comparing tagged and untagged birds in either year. When comparing within tagged birds, however, using a tied harness significantly reduced resighting rate by 53% on average compared to using an elastic harness (in all models), but stalk length effects were not statistically significant in any model considered. There was no strong evidence that the fit (relative tightness) or added tag mass affected survival, although tied tags were fitted more tightly later in the study, and birds fitted with tied tags later may have had lower survival. Overall, on a precautionary principle, deploying tags with non-elastic tied harnesses should be avoided because the necessary fit, so as not to reduce survival, is time-consuming to achieve and does not necessarily improve with experience. Geolocator tags of the recommended percentage of body mass fitted with elastic leg-loop harnesses and with short light stalks can be used without survival effects in small long-distance migrant birds.

Accelerometry reveals an impact of short-term tagging on seabird activity budgets

ABSTRACT Miniaturized data loggers have revolutionized the study of animal movement. However, data obtained from tagging could be compromised by impacts on animal welfare and behavior. We evaluated short-term (activity budgets, foraging trip metrics, overall dynamic body acceleration [ODBA] of flying, wingbeat frequency, adult mass, and nestling mass) and long-term metrics (breeding success and survival) for breeding female Black-legged Kittiwakes (Rissa tridactyla) tagged with both GPS and accelerometer tags (5.2% of body mass), birds tagged with only accelerometers (1.0% of body mass), and untagged birds. Breeding success, survival, adult mass, and nestling mass were not affected by tagging, and there were no differences in trip metrics, ODBA, and flapping frequency for birds tagged with GPS and accelerometer packages vs. only accelerometers. However, accelerometry revealed that, when tagged for 3 days with GPS and accelerometer tags, kittiwakes reduced the amount of time spent flying by 30%. Impacts of...

Effect of xylanase and a blend of essential oils on performance and Salmonella colonization of broiler chickens challenged with Salmonella Heidelberg

The present experiment examined the influence of xylanase supplementation and a blend of essential oils (EO; cinnamaldehyde and thymol) on performance and Salmonella horizontal transmission in broiler chickens challenged with Salmonella. Two thousand 1-d-old broiler chicks were randomly assigned to 5 dietary treatments (8 pens/treatment of 50 male broilers each). Four dietary treatments were challenged with Salmonella: 1) control, 2) basal diets supplemented with EO, 3) basal diet supplemented with xylanase (2,000 U/kg of feed), and 4) basal diet supplemented with a combination of EO and xylanase (2,000 U/kg of feed). One treatment served as an unchallenged control and was not supplemented with either additive. Broiler starter and finisher diets, based on wheat and soybean meal, were formulated, pelleted, and fed ad libitum. At d 1, before placement, half of the birds from each pen were tagged and dosed with Salmonella enterica serovar Heidelberg (5 × 10(5) cfu/mL). On d 42, 5 random untagged birds from each pen were killed and their ceca removed and tested for Salmonella. Performance data were analyzed as a completely randomized design using GLM. The frequency of positive Salmonella in the untagged birds was compared between treatments by using a chi-squared test of homogeneity. Challenging the birds with Salmonella had no effect (P > 0.05) on any of the measured performance parameters. Xylanase and EO supplementation improved (P < 0.05) the 42-d BW gain and feed efficiency, with no effect (P > 0.05) on feed intake, compared with that of the control treatment. Xylanase supplementation improved (P < 0.05) BW gain and feed efficiency compared with the results of EO supplementation. The combination treatment of xylanase and EO numerically improved BW gain and feed efficiency compared with the xylanase treatment. Xylanase and EO supplementation reduced (P < 0.05) the incidence of horizontal transmission of Salmonella infection between birds by 61 and 77%, respectively, compared with the control. The results of the current study suggested that dietary addition of EO and xylanase could improve broiler performance and contribute to food safety by lowering the incidence of horizontal transmission of Salmonella infection.

Telemetry‐based field studies for assessment of acute and short‐term risk to birds from spray applications of chlorpyrifos

In a program of avian field studies, radiotelemetry was combined with observations, carcass searches, residue analysis, and determination of brain acetylcholinesterase (AChE) activity to assess the acute and short-term risk posed by chlorpyrifos to birds. Studies were conducted in field crops (brassicas, Poland) and orchards (pome, Italy; citrus, Spain). In total, 25 individual applications of chlorpyrifos were studied on 13 sites. Before each application, birds were fitted with radio transmitters (with minimum stress to birds). Radiotagged birds were monitored and the avifauna observed before, during and for 7 d following each application. A total of 201 birds representing 19 species were radiotagged. In 80% of individual telemetric monitoring periods, birds remained at the study sites. No radiotagged birds showed any sign of intoxication. These included individuals who spent a major proportion of time within treated areas (some individuals located within treated area on >90% of occasions). A total of 7,238 bird sightings were recorded during constant observation during and immediately after application. An additional 4,017 sightings were recorded in 104 individual surveys during 7 d after each application. Two untagged birds (out of 11,255 bird sightings) exhibited atypical behavior for <1 min and 2 to 3 min, respectively, before flying away. This observation (for 0.02% of bird sightings) may or may not have been treatment related. Ten carcasses were recovered (none radiotagged). Residue analysis and brain AChE activity indicated that none was likely to have died from chlorpyrifos exposure. Radiotracking, supported by more traditional assessment methods, was effective for assessing impacts in the field. This extensive field program supports a conclusion that spray applications of chlorpyrifos present a low risk to birds.

Field-Testing the Suitability of a New Back-Pack Harness for Radio-Tagging Passerines

Attaching radio-tags to highly dynamic organisms can bias the data collected. The nature and extent of any bias should be understood and quantified. This is vital with an untested attachment method or when tagging a new species or age-class. The suitability of a new back-pack harness design was field tested on 39 adult thrushes (33 Blackbird Turdus merula and 6 Song Thrush T. philomelos) at a study site in England. Direct chronic effects were assessed by examination of recovered corpses and recaptured birds. The harness caused the development of a small subcutaneous lipid mass on the patagium but no epidermal abrasion or inter-scapular blistering or bruising. Indirect measures of possible chronic effects came from behavioural observation and breeding performance measures. For female birds, the attachment of a back-pack tag did not significantly reduce clutch size or egg volume compared with untagged females. Nest survival rates were also unaffected. The number and quality of young fledged by tagged females were as high as those for untagged females. Video data showed that provisioning rates of the nestlings did not differ significantly between tagged and untagged parents. The proportion of time spent brooding by tagged female Blackbirds was non-significantly higher than for untagged birds.

Home range and habitat selection by the Nutcracker Nucifraga caryocatactes during autumn in the Alps

In the Mont Avic Natural Park (NW Italian Alps), the Nutcracker Nucifraga caryocatactes occurred in coniferous forests where Arolla Pines Pinus cembra, its preferred habitat, were absent. A radiotelemetric study carried out during autumn 1992 and 1993 showed that, from September, Nutcrackers concentrated in the few Hazel Corylus avellana hedges of the rural zones of the park to collect nuts, which were eaten or stored. Individual home ranges overlapped to a high degree until October, when birds started to abandon the Hazel areas. From October onward, individual home ranges significantly expanded and their degree of overlap diminished compared to September. The home range analysis and the observations in the field suggested that the population of Nutcrackers in the park during autumn was made up of at least three different categories of birds, which displayed different ranging behaviour patterns. A few untagged birds probably stored nuts in their breeding territories, whereas all the radio‐tagged birds (n = 15) gave no indication of territorial use, since from October they either stored nuts in the coniferous woods near the Hazel hedges or abandoned the park to fly to other Hazel areas. Hence, during autumn the ranging behaviour of the Nutcrackers seems to be largely independent of their reproductive territorial system. Habitat selection analysis and transect counts revealed that birds positively selected Hazels, especially in the coniferous woods around Hazel hedges, and avoided the other coniferous forests. Nevertheless, from October some individuals reversed their habitat choices and positively selected coniferous forests (especially Mountain Pine Pinus uncinata woods) while avoiding Hazel.

Effects of Radiotagging on Breeding Merlins

We examined the impact of radiotagging on breeding merlins (Falco columbarius) in Saskatoon (Canada) between May and July, 1987-90. We compared reproductive and hatching success between 12 tagged and 71 untagged males. We also collated return rates between 21 tagged (both M and F) and 112 untagged merlins. We did not observe any long-lasting abnormal behavior in tagged birds during the postrelease period. Breeding output, hatching success, and survival did not differ significantly (P>0.05) between radio-tagged and untagged birds

Patagial tags for herring gulls: Improved durability

This paper describes a modification to the method for attaching patagial tags, which increases tag durability and reduces callousing and feather abrasion. Breeding success of wing‐tagged Herring Gulls was similar to that found in earlier studies of untagged birds at the same colony. Estimates of adult mortality and pairing change rates are presented and discussed, but comparable data for untagged birds are not available.