In the present study, the influence of stress from handling and transport on some frequently examined blood parameters of racing pigeons was evaluated. After 3 hr, there was a highly significant (P < 0.01) increase in the number as well as in the percentage of heterophils and decrease of lymphocytes. In clinical chemistries, increases of creatine kinase and glucose and a decrease of uric acid were observed. There was a mean decrease of the total white blood count of >15% that was less significant (P < 0.05). Changes in lactate dehydrogenase, basophils, and monocytes did not prove to be significant; eosinophils, aspartate aminotransferase, total protein, and the packed cell volume were not influenced by stress.

A longitudinal study was performed in order to investigate virus excretion and viraemia during a clinical outbreak of the psittacine beak and feather disease in budgerigars (Melopsittacus undulatus). Viral nucleic acid was detected in feathers, cloacal swabs and blood samples. Overall, beak and feather disease virus (BFDV) DNA was detected most commonly in feather samples, followed by cloacal swabs, and least frequently from blood samples. In most cases the viraemia was short lived and correlated with clinical signs, such as feather abnormalities. Sequence analysis of the polymerase chain reaction fragment amplified from the replicationassociated gene (ORF V1) indicated a close relationship with other BFDV isolates. Overall the highest level of nucleotide identity was found with the ORF V1 of another budgerigar isolate. Our results suggest that feather samples and cloacal swabs should be taken for polymerase chain reaction diagnosis to determine the presence of BFDV in an aviary, but that detection in these samples may not correlate well with psittacine beak and feather disease.

Many migrating birds undertake extraordinary long flights. How birds are able to perform such endurance flights of over 100-hour durations is still poorly understood. We examined energy expenditure and physiological changes in Northern Bald Ibis Geronticus eremite during natural flights using birds trained to follow an ultra-light aircraft. Because these birds were tame, with foster parents, we were able to bleed them immediately prior to and after each flight. Flight duration was experimentally designed ranging between one and almost four hours continuous flights. Energy expenditure during flight was estimated using doubly-labelled-water while physiological properties were assessed through blood chemistry including plasma metabolites, enzymes, electrolytes, blood gases, and reactive oxygen compounds. Instantaneous energy expenditure decreased with flight duration, and the birds appeared to balance aerobic and anaerobic metabolism, using fat, carbohydrate and protein as fuel. This made flight both economic and tolerable. The observed effects resemble classical exercise adaptations that can limit duration of exercise while reducing energetic output. There were also in-flight benefits that enable power output variation from cruising to manoeuvring. These adaptations share characteristics with physiological processes that have facilitated other athletic feats in nature and might enable the extraordinary long flights of migratory birds as well.

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Background In this paper, we present evidence that biologging is strongly correlated with eye irritation, with sometimes severely impairing effects. A migratory population of the Northern Bald Ibis (Geronticus eremita, NBI) is reintroduced in Europe, in course of a LIFE + project. Since 2014, all individuals have been equipped with GPS-devices. Remote monitoring allows the implementation of focussed measures against major mortality causes. Methods Initially all birds carried battery-powered devices, fixed on the lower back of the birds. Since 2016 an increasing amount of birds has been equipped with solar-powered devices, fixed on the upper back, the more sun-exposed position. In 2016, we observed opacity in the cornea of one eye (unilateral corneal opacity; UCO) during a regular health monitoring for the first time. Results By 2018, a total of 25 birds were affected by UCO, with varying intensity up to blindness. Clinical examination of the birds revealed no clear cause for the symptoms. However, only birds carrying a device on the upper back were affected (2017 up to 70% of this group). In contrast, none of the birds carrying devices on the lower back ever showed UCO symptoms. This unexpected relationship between tagging and UCO was discovered in 2017. After we took countermeasures by removing the device or repositioning it on the lower back, we observed an immediate reduction of the incidence rate without any new cases reported since January 2019. NBI roost with their head on the back, one eye closely placed to the device if it was positioned on the upper back. Thus, we conclude that the most parsimonious explanation for the symptomatology is either a repetitive slight temperature rise in the corneal tissue due to electromagnetic radiation by the GSM module of the device or a repetitive slight mechanical irritation of the corneal surface. Concrete evidence is missing so far. Meanwhile, cases of UCO were found in another NBI population. Conclusion Our observations indicate that further research in the fast-growing field of biologging is urgently needed. The findings question the positioning of devices on the upper back in birds roosting with the head on the back.