Raptor Gastroenterology

Innovative problem solving by wild falcons

Innovation (i.e., a new solution to a familiar problem, or applying an existing behavior to a novel problem1,2) plays a fundamental role in species' ecology and evolution. It can be a useful measure for cross-group comparisons of behavioral and cognitive flexibility and a proxy for general intelligence.3,4,5 Among birds, experimental studies of innovation (and cognition more generally) are largely from captive corvids and parrots,6,7,8,9,10,11,12 though we lack serious models for avian technical intelligence outside these taxa. Striated caracaras (Phalcoboenus australis) are Falconiformes, sister clade to parrots and passerines,13,14,15 and those endemic to the Falkland Islands (Malvinas) show curiosity and neophilia similar to notoriously neophilic kea parrots16,17 and face similar socio-ecological pressures to corvids and parrots.18,19 We tested wild striated caracaras as a new avian model for technical cognition and innovation using a field-applicable 8-task comparative paradigm (adapted from Rössler et al.20 and Auersperg et al.21). The setup allowed us to assess behavior, rate, and flexibility of problem solving over repeated exposure in a natural setting. Like other generalist species with low neophobia,21,22 we predicted caracaras to demonstrate a haptic approach to solving tasks, flexibly switching to new, unsolved problems and improving their performance over time. Striated caracaras performed comparably to tool-using parrots,20 nearly reaching ceiling levels of innovation in few trials, repeatedly and flexibly solving tasks, and rapidly learning. We attribute our findings to the birds' ecology, including geographic restriction, resource unpredictability, and opportunistic generalism,23,24,25 and encourage future work investigating their cognitive abilities in the wild. VIDEO ABSTRACT.

Comparative Features of the Upper Alimentary Tract in the Domestic Fowl (Gallus gallus domesticus) and Kestrel (Falco tinnunculus): A Morphological, Histochemical, and Scanning Electron Microscopic Study

The avian alimentary tract has evolved into different histologic structures to accommodate the physical and chemical features of several food types and flight requirements. We compared the esophagus, proventriculus, and gizzard of the domestic fowl, Gallus gallus domesticus (GGD) and kestrels, Falco tinnunculus (FT) using immunohistochemistry and scanning electron microscopy with various stains and lectins [Dolichos biflorus agglutinin (DBA) and Ricinus communis agglutinin I (RCA120)], and α-smooth muscle actin (α-SMA). The esophagus of GGD demonstrated thickened epithelium, muscularis mucosae, and inner circular longitudinal tunica muscularis layers; moderate outer longitudinal tunica muscularis layers; and a true crop. In contrast, the esophagus of FT showed a thin epithelium, no muscularis mucosae, moderate inner longitudinal and thick outer circular tunica muscularis layers, and no true crop. In the proventriculus, the nature of the secretion in GGD was neutral, but that of FT was acidic and neutral. In the gizzard, the muscle coat of GGD by α-SMA had no muscularis mucosae, unlike FT, which had muscularis mucosae. In summary, there are many histologic differences between GGD and FT to meet their different physiologic needs, such as feeding.

Central nervous signs, blindness and cerebral vermicosis in free-ranging peregrine falcons (Falco peregrinus) associated with aberrant larval migrations

Four free-ranging peregrine falcons (Falco peregrinus) were submitted with a history of unilateral or bilateral blindness and central nervous signs to a veterinary clinic in Germany. There were no indications of trauma or ocular disease. Likewise, other differential diagnoses for CNS signs were ruled out within the diagnostic process. The clinical diagnostic panel in live falcons included general examination, radiography, endoscopy, hematology, ophthalmoscopy and parasitological examination of the feces, blood gas analysis and blood chemistry as well as computed tomography, and magnetic resonance imaging (MRI). A complete pathological and histopathological examination was performed post-mortem. The only common finding in all birds was an infection with the nematode parasite Serratospiculum tendo. The parasite was confirmed morphologically and via PCR. In two falcons intracerebral vermicoses was suspected in MRI and confirmed in subsequent histopathology, but molecular biological identification of the parasite species failed from brain tissue. Until today, S. tendo had been reported to affect the respiratory system, the liver and different parts of the gastrointestinal tract and to cause cachexia, inappetence, regurgitation, dyspnea and general signs of illness such as lethargy, poor plumage, and reduced reproduction. Our findings indicate that aberrant migration should be considered as cause for CNS signs in falcons. As S. tendo might be a possible cause for this, CNS signs might be included in the list of clinical signs of serratospiculiasis in falcons.

Acute and Chronic Lead Exposure in Four Avian Scavenger Species in Switzerland

Despite irrefutable evidence of its negative impact on animal behaviour and physiology, lethal and sublethal lead poisoning of wildlife is still persistent and widespread. For scavenging birds, ingestion of ammunition, or fragments thereof, is the major exposure route. In this study, we examined the occurrence of lead in four avian scavengers of Switzerland and how it differs between species, regions, and age of the bird. We measured lead concentration in liver and bone of the two main alpine avian scavengers (golden eagle Aquila chrysaetos and bearded vulture Gypaetus barbatus) over the entire area of the Swiss Alps and two of the main avian scavengers occurring in the lowlands of Switzerland (red kite Milvus milvus and common raven Corvus corax). Of those four species, only the bearded vulture is an obligate scavenger. We found that lead burdens in the two alpine avian scavengers were higher than those found for the same species elsewhere in Europe or North America and reached levels compatible with acute poisoning, whereas lead burdens of the two lowland avian scavengers seemed to be lower. Several golden eagles, but only one red kite with abnormally high bone lead concentrations were found. In all four species, a substantial proportion of birds had elevated levels which presumably represent recent (liver lead levels) or past (bone lead levels) uptake of sublethal doses of lead.

Surgical Removal of a Ventricular Foreign Body in a Captive African Black-footed Penguin ( Spheniscus demersus )

Anterior gastrointestinal tract obstruction by a foreign body has been reported in several avian species, most commonly in captive birds. It is often associated with behavioral issues that lead to compulsive consumption of bedding materials or bright moving objects. In penguins, foreign bodies are most commonly identified at necropsy and often are found in the ventriculus because of anatomic characteristics of the species. A captive African black-footed penguin ( Spheniscus demersus ) was diagnosed with a ventricular foreign body. The anatomic and physiologic differences that should be taken into account when surgically removing a ventricular foreign body in a penguin are described. These differences include the caudal location in the coelom and the large size of the ventriculus in proportion to the penguin's body size; the presence of a simple stomach, uniform in thickness and lacking muscular development; a simple gastrointestinal cycle (gastric contraction); and variability in pH of stomach contents. No complications were observed after surgery, and the bird recovered completely. Management of foreign bodies in birds should be based on the clinical signs of the individual bird, the species affected and its anatomic characteristics, the nature and location of the foreign body, available tools, and the preference and experience of the surgeon. This particular case demonstrates that the most indicated and preferred method is not always possible and that knowledge of biologic, anatomic, and physiologic differences of the species may allow the use of an alternative and more invasive approach with favorable outcomes.

Comparative analysis reveals loss of the appetite-regulating peptide hormone ghrelin in falcons

Ghrelin and leptin are key peripherally secreted appetite-regulating hormones in vertebrates. Here we consider the ghrelin gene (GHRL) of birds (class Aves), where it has been reported that ghrelin inhibits rather than augments feeding. Thirty-one bird species were compared, revealing that most species harbour a functional copy of GHRL and the coding region for its derived peptides ghrelin and obestatin. We provide evidence for loss of GHRL in saker and peregrine falcons, and this is likely to result from the insertion of an ERVK retrotransposon in intron 0. We hypothesise that the loss of anorexigenic ghrelin is a predatory adaptation that results in increased food-seeking behaviour and feeding in falcons.

New specimens of Yanornis indicate a piscivorous diet and modern alimentary canal

A crop adapted for an herbivorous diet of seeds has previously been documented in the Early Cretaceous birds Sapeornis and Hongshanornis. Here we report on several specimens of Yanornis that preserve a crop containing fish. One specimen preserves two whole fish in the oesophagus, indicating that Early Cretaceous birds shared trophic specializations with Neornithes for the increased energetic demands of flight – namely the storing of food for later consumption when the stomach is full. Whole fish also indicate that despite their presence, teeth were not used to orally process food, suggesting the hypertrophied dentition in this taxon were utilized in prey capture. The presence of macerated fish bones in the crop of other specimens indicates the highly efficient advanced muscular system of peristalsis responsible for moving ingested items between different segments of the alimentary canal was also in place. Despite the fact many features of the modern avian alimentary canal are inferred to compensate for the absence of teeth in birds (expandable oesophagus, grinding gizzard), the derived alimentary canal was apparently present in toothed Cretaceous birds. Although Yanornis was considered to have switched their diet from piscivorous to herbivorous, based on position and morphology we reinterpret the gastroliths reported in one specimen as sand impacted in the intestines, and reconstruct the taxon as primarily piscivorous. This is a novel interpretation for fossilized gastroliths, and the first documentation of this condition in the fossil record.

Chronic dermatitis caused by Lactobacillus jensenii infection in a blue and gold macaw (Ara ararauna)

CASE DESCRIPTION

A 5-year-old sexually intact female blue and gold macaw (Ara ararauna) was evaluated because of a swelling on the right side of the face and irritated area on the ventral aspect of the keel.

CLINICAL FINDINGS

Clinical findings were consistent with dermatitis (right facial lesion) and a coalescing subdermal granuloma (ventral keel lesion). Hematologic analysis revealed monocytosis and mild anemia. Histologic evaluation of the ventral keel lesion revealed evidence of chronic heterophilic dermatitis with multinucleated giant cells and bacterial rods and cocci. An unspeciated gram-positive rod-shaped bacterium was isolated via aerobic bacterial culture. Results of bacterial biochemical tests suggested the organism was a type of Actinomyces. A 16S rRNA gene sequence analysis was performed; results indicated the organism was Lactobacillus jensenii.

TREATMENT AND OUTCOME

Extensive surgical debridement of the branching granuloma, which extended throughout the length of the keel, followed by long-term treatment with ciprofloxacin and clindamycin provided full resolution of clinical signs. No recrudescence of clinical signs was evident for up to 18 months after the initial evaluation.

CLINICAL RELEVANCE

To the authors' knowledge, this is the first report of Lactobacillus-associated dermatitis or subdermal granuloma in the scientific literature and the second report of L jensenii in avian species. Use of 16S rRNA gene sequence analysis was instrumental in the identification of this fastidious organism, indicating the method's usefulness as a diagnostic tool.

Vultures of the seas: hyperacidic stomachs in wandering albatrosses as an adaptation to dispersed food resources, including fishery wastes

Animals are primarily limited by their capacity to acquire food, yet digestive performance also conditions energy acquisition, and ultimately fitness. Optimal foraging theory predicts that organisms feeding on patchy resources should maximize their food loads within each patch, and should digest these loads quickly to minimize travelling costs between food patches. We tested the prediction of high digestive performance in wandering albatrosses, which can ingest prey of up to 3 kg, and feed on highly dispersed food resources across the southern ocean. GPS-tracking of 40 wandering albatrosses from the Crozet archipelago during the incubation phase confirmed foraging movements of between 475–4705 km, which give birds access to a variety of prey, including fishery wastes. Moreover, using miniaturized, autonomous data recorders placed in the stomach of three birds, we performed the first-ever measurements of gastric pH and temperature in procellariformes. These revealed surprisingly low pH levels (average 1.50±0.13), markedly lower than in other seabirds, and comparable to those of vultures feeding on carrion. Such low stomach pH gives wandering albatrosses a strategic advantage since it allows them a rapid chemical breakdown of ingested food and therefore a rapid digestion. This is useful for feeding on patchy, natural prey, but also on fishery wastes, which might be an important additional food resource for wandering albatrosses.

Copper pellets simulating oral exposure to copper ammunition: absence of toxicity in American kestrels (Falco sparverius)

To evaluate the potential toxicity of copper (Cu) in raptors that may consume Cu bullets, shotgun pellets containing Cu, or Cu fragments as they feed on wildlife carcasses, we studied the effects of metallic Cu exposure in a surrogate, the American kestrel (Falco sparverius). Sixteen kestrels were orally administered 5 mg Cu/g body mass in the form of Cu pellets (1.18-2.00 mm in diameter) nine times during 38 days and 10 controls were sham gavaged on the same schedule. With one exception, all birds retained the pellets for at least 1 h, but most (69%) regurgitated pellets during a 12-h monitoring period. Hepatic Cu concentrations were greater in kestrels administered Cu than in controls, but there was no difference in Cu concentrations in the blood between treated and control birds. Concentration of the metal-binding protein metallothionein was greater in male birds that received Cu than in controls, whereas concentrations in female birds that received Cu were similar to control female birds. Hepatic Cu and metallothionein concentrations in kestrels were significantly correlated. Histopathologic alterations were noted in the pancreas of four treated kestrels and two controls, but these changes were not associated with hepatic or renal Cu concentrations, and no lesions were seen in other tissues. No clinical signs were observed, and there was no treatment effect on body mass; concentrations of Cu, hemoglobin, or methemoglobin in the blood; or Cu concentrations in kidney, plasma biochemistries, or hematocrit. Based on the parameters we measured, ingested Cu pellets pose little threat to American kestrels (and presumably phylogenetically related species), although the retention time of pellets in the stomach was of relatively short duration. Birds expected to regurgitate Cu fragments with a frequency similar to kestrels are not likely to be adversely affected by Cu ingestion, but the results of our study do not completely rule out the potential for toxicity in species that might retain Cu fragments for a longer time.