Homing pigeons externally exposed to Deepwater Horizon crude oil change flight performance and behavior

The Deepwater Horizon oil spill was the largest in U.S. history, contaminating thousands of miles of coastal habitat and affecting the lives of many avian species. The Gulf of Mexico is a critical bird migration route area and migrants that were oiled but did not suffer mortality as a direct result of the spill faced unpredictable fates. This study utilized homing pigeons as a surrogate species for migratory birds to investigate the effects a single low level external oiling event has on the flight performance and behavior of birds flying repeated 161 km flights. Data from GPS data loggers showed that lightly oiled pigeons changed their flight paths, increased their flight durations by 2.6 fold, increased their flight distances by 28 km and subsequently decreased their route efficiencies. Oiled birds also exhibited reduced rate of weight gain between flights. Our data suggest that contaminated birds surviving the oil spill may have experienced flight impairment and reduced refueling abilities, likely reducing overall migration speed. Our findings contribute new information on how oil spills affect avian species, as the effects of oil on the flight behavior of long distance free-flying birds have not been previously described.

Ingestion of a Single 2.3 mm Lead Pellet by Laying Roller Pigeon Hens Reduces Egg Size and Adversely Affects F1 Generation Hatchlings

Many aquatic and terrestrial avian species inadvertently ingest lead (Pb) in the form of spent or fragmented ammunition, mistaking it for food or grit. Previous studies in our laboratory have shown that ingestion of even a single 45-mg pellet can significantly increase blood-Pb levels and significantly inhibit the enzyme delta aminolevulinic-acid dehydratase (δ-ALAD) for a period of greater than 4 weeks. In the current study, proven breeder pairs of domestic Roller pigeons were housed in individual cages. The hens were orally gavaged with dH₂O vehicle, a single #9 Pb pellet (2.0 mm/45 mg) or a single #7.5 Pb pellet (2.3 mm/95 mg), placed back with the cock bird and allowed to mate for two consecutive clutches. The eggs were monitored for fertilization, shell damage, egg weight, and length during the 16- to 18-day incubation period. Hatchlings remained with the hen and cock through the weaning period (28-35 days post hatch) and were monitored for weight, development, and mortality. Weanling blood was collected for blood-Pb levels, δ-ALAD activity, red blood cell counts, total protein, and packed cell volume. Following euthanasia, weanling liver, spleen, kidney, sciatic nerve, thymus, and brain were collected for histopathology. Egg weight and length were significantly decreased in the #7.5 Pb pellet treatment group for the first clutch, and hatchling weight 7 days post hatch also was significantly less in the #7.5 Pb pellet treatment group during the first clutch. Histopathologic analysis showed increased lesions in liver, kidney, spleen, and thymus of the Pb-treated weanlings, during both the first and second clutch compared with the non-Pb-treated weanlings. These data suggest that maternal consumption of a single 95-mg Pb pellet can adversely impact egg size and hatchling organ development.

Are baboons learning "orthographic" representations? Probably not

The ability of Baboons (papio papio) to distinguish between English words and nonwords has been modeled using a deep learning convolutional network model that simulates a ventral pathway in which lexical representations of different granularity develop. However, given that pigeons (columba livia), whose brain morphology is drastically different, can also be trained to distinguish between English words and nonwords, it appears that a less species-specific learning algorithm may be required to explain this behavior. Accordingly, we examined whether the learning model of Rescorla and Wagner, which has proved to be amazingly fruitful in understanding animal and human learning could account for these data. We show that a discrimination learning network using gradient orientation features as input units and word and nonword units as outputs succeeds in predicting baboon lexical decision behavior-including key lexical similarity effects and the ups and downs in accuracy as learning unfolds-with surprising precision. The models performance, in which words are not explicitly represented, is remarkable because it is usually assumed that lexicality decisions, including the decisions made by baboons and pigeons, are mediated by explicit lexical representations. By contrast, our results suggest that in learning to perform lexical decision tasks, baboons and pigeons do not construct a hierarchy of lexical units. Rather, they make optimal use of low-level information obtained through the massively parallel processing of gradient orientation features. Accordingly, we suggest that reading in humans first involves initially learning a high-level system building on letter representations acquired from explicit instruction in literacy, which is then integrated into a conventionalized oral communication system, and that like the latter, fluent reading involves the massively parallel processing of the low-level features encoding semantic contrasts.

In vivo measurement of T1 and T2 relaxation times in awake pigeon and rat brains at 7T

PURPOSE

Establishment of regional longitudinal (T₁ ) and transverse (T₂ ) relaxation times in awake pigeons and rats at 7T field strength. Regional differences in relaxation times between species and between two different pigeon breeds (homing pigeons and Figurita pigeons) were investigated.

METHODS

T₁ and T₂ relaxation times were determined for nine functionally equivalent brain regions in awake pigeons and rats using a multiple spin-echo saturation recovery method with variable repetition time and a multi-slice/multi-echo sequence, respectively. Optimized head fixation and habituation protocols were applied to accustom animals to the scanning conditions and to minimize movement.

RESULTS

The habituation protocol successfully limited movement of the awake animals to a negligible minimum, allowing reliable measurement of T₁ and T₂ values within all regions of interest. Significant differences in relaxation times were found between rats and pigeons but not between different pigeon breeds.

CONCLUSION

The obtained T₁ and T₂ values for awake pigeons and rats and the optimized habituation protocol will augment future MRI studies with awake animals. The differences in relaxation times observed between species underline the importance of the acquisition of T₁ /T₂ values as reference points for specific experiments. Magn Reson Med 79:1090-1100, 2018. © 2017 International Society for Magnetic Resonance in Medicine.

Responses of Oral 2,4,6-Trinitrotoluene (TNT) Exposure to the Common Pigeon (Columba livia): A Phylogenic and Methodological Comparison

Considerable concentrations of the explosive, 2,4,6-trinitrotoluene (TNT) have been found in the soil at many installations where explosives have been used, manufactured, assembled, or destroyed. To evaluate risk to avian receptors, measures of exposure are compared with a threshold level of sublethal toxicity. To date, a single feeding study has evaluated the responses of oral TNT exposure to birds with equivocal results regarding sublethal effects. The present study followed a controlled dosing regime comprising four dose groups and a control (200, 120, 70, 20, and 0 mg TNT/kg body weight [bw]-day) in the common pigeon ( Columba livia) for 60 days. Overt signs of toxicity occurred with both sexes between 2 and 3 weeks of exposure. Signs included weight loss, neuromuscular effects (e.g., ataxia, tremors, etc.), and scant red feces (chromaturia). Emetic events following dosing were common and proportional to dose; however, attempts to quantify vomitus compound concentration suggests that birds were marginally successful at removing TNT following administration. Eight of 12 and 2 of 12 males and females died or were moribund in the 200 and 120 mg/kg-day groups, respectively. Changes in hematological parameters, liver, kidney, and ovary weights were related to treatment. Dose-related changes in plasma albumin and sodium concentrations were also observed. These results suggest that subchronic exposure to TNT can adversely affect the central nervous system and hematological parameters in birds. Chemical analysis of blood detected concentrations of the two primary reduction metabolites, but not parent compound, suggesting that toxicity may be due to the bioaccumulation of a toxic intermediate.

Genomic evidence of demographic fluctuations and lack of genetic structure across flyways in a long distance migrant, the European turtle dove

BACKGROUND

Understanding how past climatic oscillations have affected organismic evolution will help predict the impact that current climate change has on living organisms. The European turtle dove, Streptopelia turtur, is a warm-temperature adapted species and a long distance migrant that uses multiple flyways to move between Europe and Africa. Despite being abundant, it is categorized as vulnerable because of a long-term demographic decline. We studied the demographic history and population genetic structure of the European turtle dove using genomic data and mitochondrial DNA sequences from individuals sampled across Europe, and performing paleoclimatic niche modelling simulations.

RESULTS

Overall our data suggest that this species is panmictic across Europe, and is not genetically structured across flyways. We found the genetic signatures of demographic fluctuations, inferring an effective population size (Ne) expansion that occurred between the late Pleistocene and early Holocene, followed by a decrease in the Ne that started between the mid Holocene and the present. Our niche modelling analyses suggest that the variations in the Ne are coincident with recent changes in the availability of suitable habitat.

CONCLUSIONS

We argue that the European turtle dove is prone to undergo demographic fluctuations, a trait that makes it sensitive to anthropogenic impacts, especially when its numbers are decreasing. Also, considering the lack of genetic structure, we suggest all populations across Europe are equally relevant for conservation.

Feral Pigeons (Columba livia) Prefer Genetically Similar Mates despite Inbreeding Depression

Avoidance of mating between related individuals is usually considered adaptive because it decreases the probability of inbreeding depression in offspring. However, mating between related partners can be adaptive if outbreeding depression is stronger than inbreeding depression or if females gain inclusive fitness benefits by mating with close kin. In the present study, we used microsatellite data to infer the parentage of juveniles born in a French colony of feral pigeons, which allowed us to deduce parent pairs. Despite detectable inbreeding depression, we found that pairwise relatedness between mates was significantly higher than between nonmates, with a mean coefficient of relatedness between mates of 0.065, approximately half the theoretical value for first cousins. This higher relatedness between mates cannot be explained by spatial genetic structure in this colonial bird; it therefore probably results from an active choice. As inbreeding but not outbreeding depression is observed in the study population, this finding accords with the idea that mating with genetically similar mates can confer a benefit in terms of inclusive fitness. Our results and published evidence suggest that preference for related individuals as mates might be relatively frequent in birds.

Suboptimal Choice in Pigeons: Stimulus Value Predicts Choice over Frequencies

Pigeons have shown suboptimal gambling-like behavior when preferring a stimulus that infrequently signals reliable reinforcement over alternatives that provide greater reinforcement overall. As a mechanism for this behavior, recent research proposed that the stimulus value of alternatives with more reliable signals for reinforcement will be preferred relatively independently of their frequencies. The present study tested this hypothesis using a simplified design of a Discriminative alternative that, 50% of the time, led to either a signal for 100% reinforcement or a blackout period indicative of 0% reinforcement against a Nondiscriminative alternative that always led to a signal that predicted 50% reinforcement. Pigeons showed a strong preference for the Discriminative alternative that remained despite reducing the frequency of the signal for reinforcement in subsequent phases to 25% and then 12.5%. In Experiment 2, using the original design of Experiment 1, the stimulus following choice of the Nondiscriminative alternative was increased to 75% and then to 100%. Results showed that preference for the Discriminative alternative decreased only when the signals for reinforcement for the two alternatives predicted the same probability of reinforcement. The ability of several models to predict this behavior are discussed, but the terminal link stimulus value offers the most parsimonious account of this suboptimal behavior.

Does allopreening control avian ectoparasites?

For birds, the first line of defence against ectoparasites is preening. The effectiveness of self-preening for ectoparasite control is well known. By contrast, the ectoparasite control function of allopreening-in which one birds preens another-has not been rigorously tested. We infested captive pigeons with identical numbers of parasitic lice, and then compared rates of allopreening to the abundance of lice on the birds over time. We documented a negative relationship between rates of allopreening and the number of lice on birds. Moreover, we found that allopreening was a better predictor of louse abundance than self-preening. Our data suggest that allopreening may be a more important means of ectoparasite defence than self-preening when birds live in groups. Our results have important implications for the evolution of social behaviour.

Perceptual Grouping in Pigeons

Animal studies reveal that many species perceive partially occluded objects in the same way as do humans. Pigeons have been a notable exception. We re-investigated this anomaly of pigeon perception using a different approach from previous studies. With our method, we show that pigeons perceive occluded objects in the same manner as do other species. In addition, we report that pigeons can recognize perceptually transparent surfaces when the effect is induced by the same perceptual mechanisms as occlusion. These results give behavioral evidence that the perception of both occlusion and transparency is a common visual function shared by pigeons and humans, despite the structural differences between their visual systems.

Does the Use of Natural Stimuli Facilitate Amodal Completion in Pigeons?

Three experiments were carried out to investigate whether amodal completion in pigeons can be facilitated by the use of colour photographs instead of highly artificial stimuli such as geometrical shapes. Ten pigeons were trained in a go/no-go procedure to discriminate between photographs of complete and of incomplete pigeon figures. In the subsequent test, the birds classified pictures of partly occluded pigeons as though they were complete (experiment 1). However, we found evidence that classification was based on spurious stimulus features that paralleled the intended class rule of figural completeness versus incompleteness. In particular, classification was shown to be guided by white background gaps that separated the parts of the fragmented pigeon figures (experiment 2), as well as by cues related to overall Gestalt (experiment 3). In summary, the present results indicate that the use of more natural stimuli such as photographs instead of geometrical shapes is insufficient for providing amodal completion in pigeons. It is suggested that a combination of various cues, including, eg, 3-D information and common motion in addition to surface and contour properties, may be required to induce a perceptual bias favouring visual completion of occluded portions.

The Role of Edges in Object Recognition by Pigeons

In three experiments, we explored how pigeons use edges, corresponding to orientation and depth discontinuities, in visual recognition tasks. In experiment 1, we compared the pigeon's ability to recognize line drawings of four different geons when trained with shaded images. The birds were trained with either a single view or five different views of each object. Because the five training views had markedly different appearances and locations of shaded surfaces, reflectance edges, etc, the pigeons might have been expected to rely more on the orientation and depth discontinuities that were preserved over rotation and in the line drawings. In neither condition, however, was there any transfer from the rendered images to the outline drawings. In experiment 2, some pigeons were trained with line drawings and shaded images of the same objects associated with the same response (consistent condition), whereas other pigeons were trained with a line drawing and a shaded image of two different objects associated with the same response (inconsistent condition). If the pigeons perceived any correspondence between the stimulus types, then birds in the consistent condition should have learned the discrimination more quickly than birds in the inconsistent condition. But, there was no difference in performance between birds in the consistent and inconsistent conditions. In experiment 3, we explored pigeons' processing of edges by comparing their discrimination of shaded images or line drawings of four objects. Once trained, the pigeons were tested with planar rotations of those objects. The pigeons exhibited different patterns of generalization depending on whether they were trained with line drawings or shaded images. The results of these three experiments suggest that pigeons may place greater importance on surface features indicating materials, such as food or water. Such substances do not have definite boundaries—cued by edges—which are thought to be central to human recognition.

Parent-offspring behavior of Jambu fruit doves (Ptilinopus jambu)

Fruit doves (Ptilinopus) constitute a genus of small to medium-sized, brightly colored arboreal birds, whose diets consist entirely of fruit. Little is known about the behavior of fruit doves because most species inhabit dense forests and are difficult to observe in the wild. This study describes the parental behavior of Jambu fruit dove pairs (Ptilinopus jambu) in a captive breeding program at the Saint Louis Zoo. Continuous video recordings were made of three pairs which raised a total of eight squabs over 2 years; daily rates of parental and squab behaviors were quantified. Overall, females were present at the nest, brooded their squabs, pecked, and attempted feedings more often than males. Parents also cared for their squabs at different times throughout the day. Males fed and brooded squabs during the middle of the day, while females fed throughout the day and brooded in the morning, evening, and overnight. Feeding rates were lower than those described for seed-eating doves (Columbinae), with hours between consecutive feedings, and squabs rarely begged before feeding events. Most squab behaviors involved initiating or terminating brooding and self-preening. These behaviors increased as squabs approached fledging, and coincided with a shift from full to partial brooding, and a decrease in parental allopreening. Older squabs also initiated feeding less frequently. Together, these data provide the first description of parental behavior in a Ptilinopus fruit dove. The results of this study may help improve captive breeding efforts, which are likely to become increasingly important for future conservation and reintroduction programs.

Collective Decision-Making in Homing Pigeons: Larger Flocks Take Longer to Decide but Do Not Make Better Decisions

Social animals routinely are challenged to make consensus decisions about movement directions and routes. However, the underlying mechanisms facilitating such decision-making processes are still poorly known. A prominent question is how group members participate in group decisions. We addressed this question by examining how flocks of homing pigeons (Columba livia) decide their homing direction. We released newly formed flocks varying in size and determined the time taken to choose a homing direction (decision-making period) and the accuracy of that choice. We found that the decision-making period increases exponentially with flock size, which is consistent with a participatory decision-making process. We additionally found that there is no effect of flock size on the accuracy of the decisions made, which does not match with current theory for democratic choices of flight directions. Our combined results are better explained by a participatory choice of leaders that subsequently undertake the flock directional decisions. However, this decision-making model would only entirely fit with our results if leaders were chosen based on traits other than their navigational experience. Our study provides rare empirical evidence elucidating decision-making processes in freely moving groups of animals.

Detection and discrimination of complex sounds by pigeons (Columba livia)

Auditory scene analysis is the process by which sounds are separated and identified from each other and from the background to make functional auditory objects. One challenge in making these psychological units is that complex sounds often continuously differ in composition over their duration. Here we examined the acoustic basis of complex sound processing in four pigeons by evaluating their performance in an ongoing same/different (S/D) task. This provided an opportunity to investigate avian auditory processing in a non-vocal learning, non-songbird. These pigeons were already successfully discriminating 18.5 s sequences of all different 1.5 s sounds (ABCD…) from sequences of one sound repeating (AAAA…, BBBB…, etc.) in a go/no-go procedure. The stimuli for these same/different sequences consisted of 504 tonal sounds (36 chromatic notes×14 different instruments), 36 pure tones, and 72 complex sounds. Not all of these sounds were equally effective in supporting S/D discrimination. As identified by a stepwise regression modeling of ten acoustic properties, tonal and complex sounds with intermediate levels of acoustic content tended to support better discrimination. The results suggest that pigeons have the auditory and cognitive capabilities to recognize and group continuously changing sound elements into larger functional units that can serve to differentiate long sequences of same and different sounds.

Feature- versus rule-based generalization in rats, pigeons and humans

Humans can spontaneously create rules that allow them to efficiently generalize what they have learned to novel situations. An enduring question is whether rule-based generalization is uniquely human or whether other animals can also abstract rules and apply them to novel situations. In recent years, there have been a number of high-profile claims that animals such as rats can learn rules. Most of those claims are quite weak because it is possible to demonstrate that simple associative systems (which do not learn rules) can account for the behavior in those tasks. Using a procedure that allows us to clearly distinguish feature-based from rule-based generalization (the Shanks-Darby procedure), we demonstrate that adult humans show rule-based generalization in this task, while generalization in rats and pigeons was based on featural overlap between stimuli. In brief, when learning that a stimulus made of two components ("AB") predicts a different outcome than its elements ("A" and "B"), people spontaneously abstract an opposites rule and apply it to new stimuli (e.g., knowing that "C" and "D" predict one outcome, they will predict that "CD" predicts the opposite outcome). Rats and pigeons show the reverse behavior-they generalize what they have learned, but on the basis of similarity (e.g., "CD" is similar to "C" and "D", so the same outcome is predicted for the compound stimulus as for the components). Genuinely rule-based behavior is observed in humans, but not in rats and pigeons, in the current procedure.

Personality and morphological traits affect pigeon survival from raptor attacks

Personality traits have recently been shown to impact fitness in different animal species, potentially making them similarly relevant drivers as morphological and life history traits along the evolutionary pathways of organisms. Predation is a major force of natural selection through its deterministic effects on individual survival, but how predation pressure has helped to shape personality trait selection, especially in free-ranging animals, remains poorly understood. We used high-precision GPS tracking to follow whole flocks of homing pigeons (Columba livia) with known personalities and morphology during homing flights where they were severely predated by raptors. This allowed us to determine how the personality and morphology traits of pigeons may affect their risk of being predated by raptors. Our survival model showed that individual pigeons, which were more tolerant to human approach, slower to escape from a confined environment, more resistant to human handling, with larger tarsi, and with lighter plumage, were more likely to be predated by raptors. We provide rare empirical evidence that the personality of prey influences their risk of being predated under free-ranging circumstances.

Asymmetry in the discrimination of quantity: The role of stimulus generalization

In order to evaluate 1 account for the asymmetry that has been found with discriminations based on stimulus magnitude, in 5 autoshaping experiments, 2 groups of pigeons received a discrimination between 5 and 20 squares presented on a TV screen. One group received a 20+/5- discrimination, with food signaled by 20 squares but not 5 squares; the other group received the opposite discrimination, 5+/20-. The 20+/5- discrimination was acquired more readily than 5+/20- in Experiments 1, 3a, 3b, and 4. For Experiment 1, the screen was white for the intertrial interval (ITI) and the stimuli were black squares on a white background; for Experiment 3a, the screen was black for the ITI and the stimuli were black squares on a white background; and for Experiments 3b and 4, the screen was white for the ITI and the stimuli were white squares on a black background. In Experiment 2, the stimuli were black squares on a white background, but they were separated by an ITI in which 288 black squares were presented against a white background. The 20+/5- discrimination was now acquired more slowly than the 5+/20- discrimination. The asymmetry in the acquisition of the magnitude discriminations in each experiment is attributed to inhibition being associated with the stimuli present during the ITI. The generalization of this inhibition, along a dimension related to the number of squares on the screen, is then assumed to disrupt the acquisition of 1 discrimination to a greater extent than the other.

Extinction and spontaneous recovery of spatial behavior in pigeons

We investigated extinction and spontaneous recovery of spatial associations using a landmark-based appetitive search task in a touchscreen preparation with pigeons. Four visual landmarks (A, B, C, and D) were separately established as signals of a hidden reinforced target among an 8 × 7 array of potential target locations. The target was located above landmarks (LM) A and C and below B and D. After conditioning, A and B were extinguished. Responding to A and C was assessed on probe tests 2 days following extinction, whereas, B and D were tested 14 days after extinction. We observed spontaneous recovery from spatial extinction following a 14-day, but not a 2-day, postextinction retention interval. Furthermore, by plotting the spatial distribution of responding across the X and Y axes during testing, we found that spontaneous recovery of responding to the target in our task was due to enhanced spatial control (i.e., a change in the overall distribution of responses) following the long delay to testing. These results add spatial extinction and spontaneous recovery to the list of findings supporting the assertion that extinction involves new learning that attenuates the originally acquired response, and that original learning of the spatial relationship between paired events survives extinction. (PsycINFO Database Record

Cues indicating location in pigeon navigation

Domesticated Rock Pigeons (Columba livia f. domestica) have been selected for returning home after being displaced. They appear to use many of the physical cue sources available in the natural environment for Map-and-Compass navigation. Two compass mechanisms that have been well documented in pigeons are a time-compensated sun compass and a magnetic inclination compass. Location-finding, or map, mechanisms have been more elusive. Visual landmarks, magnetic fields, odors, gravity and now also infrasound have been proposed as sources of information on location. Even in highly familiar locations, pigeons appear to neither use nor need landmarks and can even return to the loft while wearing frosted lenses. Direct and indirect evidence indicates magnetic field information influences pigeon navigation in ways that are consistent with magnetic map components. The role of odors is unclear; it might be motivational in nature rather than navigational. The influence of gravity must be further analyzed. Experiments with infrasound have been interpreted in the sense that they provide information on the home direction, but this hypothesis is inconsistent with the Map-and-Compass Model. All these factors appear to be components of a multifactorial system, with the pigeons being opportunistic, preferring those cues that prove most suitable in their home region. This has made understanding the roles of individual cues challenging.

Strange Birds: Ornithology and the Advent of the Collared Dove in Post-World War II Germany

In this paper I study the engagement of German ornithologists with the Collared Dove, a bird species of Asian origin that spread massively throughout Central Europe in the 1940s and 1950s. Never before had the spread of a single species attracted so much attention from European ornithologists. Ornithologists were not only fascinated by the exotic origin of the bird, but even more so by the unprecedented rapidity of its expansion. As it is argued in the paper, the advent of the bird created an outstanding opportunity for ornithologists to study the process of biogeographic range expansion. The paper traces how knowledge on the dove's expansion took shape in the social, discursive, and material practices of a large-scale observation campaign of German ornithologists (both amateurs and academics). The paper also argues that ornithologists' observation practices have contributed to the construction of a benevolent cultural image of the Collared Dove. This sets the case of the Collared Dove apart from many recent debates in which newly arriving species have been framed as a threat to biodiversity. The paper contributes both to a historical understanding of scientific fieldwork as well as of the role of scientific knowledge in the shaping of cultural meanings of animals.

Lab-on-a-bird: biophysical monitoring of flying birds

The metabolism of birds is finely tuned to their activities and environments, and thus research on avian systems can play an important role in understanding organismal responses to environmental changes. At present, however, the physiological monitoring of bird metabolism is limited by the inability to take real-time measurements of key metabolites during flight. In this study, we present an implantable biosensor system that can be used for continuous monitoring of uric acid levels of birds during various activities including flight. The system consists of a needle-type enzymatic biosensor for the amperometric detection of uric acid in interstitial fluids. A lightweight two-electrode potentiostat system drives the biosensor, reads the corresponding output current and wirelessly transfers the data or records to flash memory. We show how the device can be used to monitor, in real time, the effects of short-term flight and rest cycles on the uric acid levels of pigeons. In addition, we demonstrate that our device has the ability to measure uric acid level increase in homing pigeons while they fly freely. Successful application of the sensor in migratory birds could open up a new way of studying birds in flight which would lead to a better understanding of the ecology and biology of avian movements.