This study determined the distribution of phenol derivatives in the organisms of waterbirds and the factors influencing their bioaccumulation and affinity to specific tissues. Concentrations of bisphenol A (BPA), 4-tert-octylphenol (4-t-OP) and 4-nonylphenol (4-NP) were determined in the brains, subcutaneous fat, kidneys, livers and pectoral muscles of goosanders Mergus merganser (GO), long-tailed ducks Clangula hyemalis (LO) and razorbills Alca torda (RA). The birds came from the winter by-catch (2014-2016) in the Southern Baltic. Different distribution routes of individual phenol derivatives in the birds were established, most likely due to their ability to bind to proteins and/or dissolve in lipids. BPA and 4-NP accumulated most in the muscles (BPA <2.0-223.0 ng^.g^-1 dw, 4-NP 26.0-476.4 ng^.g^-1 dw), livers (BPA <2.0-318.2 ng^.g^-1 dw, 4-NP 60.7-525.8 ng^.g^-1 dw), and kidneys (BPA <2.0-836.1 ng^.g^-1 dw, 4-NP 29.3-469.2 ng^.g^-1 dw), while 4-t-OP was stored mainly in the brains (2.6-341.1 ng^.g^-1 dw), subcutaneous fat (0.7-173.7 ng^.g^-1 dw) and livers (<0.5-698.8 ng^.g^-1 dw). The liver was the only organ where all compounds showed a positive correlation with each other and alkylphenols were also positively correlated with each other in tissues with high fat content (brains and subcutaneous fat), and negatively in muscles. Despite the different trophic levels of birds, the concentrations of phenol derivatives in the tissues between individual species in most cases did not differ significantly. However, between the species on a similar trophic level, the higher biomagnification coefficient was calculated for LO feeding on benthos, and the lower for RA feeding on pelagic fish (p < 0.05). The good condition of birds, resulting in large intestinal fat stores, promoted on the one hand the penetration of phenol derivatives from the intestine to the liver, and on the other hand their accumulation in subcutaneous fat, thereby protecting the brain.

The aim of the present study was to determine the concentrations of nonylphenols (NPs) and 4-t-octylphenol (4tOP) in the muscles, liver, and kidneys of selected waterbird species. Three species with different feeding habits were selected, i.e., greater scaup (Aythya marila), great crested grebe (Podiceps cristatus), and great cormorant (Phalacrocorax carbo) to investigate the potential effects of diet on the level of contaminants tested. The determination and quantification of analytes were performed using gas chromatography with mass spectrometric detection (GC-MS). The highest NP concentrations were noted in the kidneys of greater scaups and great crested grebes (208.3 and 160.8 μg kg^-1 ww, resp.), which were six to fourteen-fold higher than those in the muscles (15.0 and 25.6 μg kg^-1 ww, resp.) and livers (22.9 and 13.8 μg kg^-1 ww, resp.) of these species. In greater scaups, the mean concentration of NPs in the livers was lower than in the muscles, while in great crested grebes, it was the opposite and higher concentrations were noted in the muscles. The mean concentrations of NPs in the muscles and livers of great cormorants were at similarly low levels (12.5 and 9.7 μg kg^-1 ww, resp.). The concentrations of 4tOP in all samples were low, ranging from <LOQ to 0.29 μg kg^-1 ww. The results of our study indicated that sex and diet did not affect the NP tissue concentrations in different waterbird species, but the phenological period (migration vs breeding) might influence the contamination levels in the kidneys.

The possibility of sex identification of birds has substantial importance for studies on different aspects of bird ecology and behaviour. Using discriminant functions is becoming increasingly popular in studies of bird species that are monomorphic in plumage characteristics because they are cheap, hardly invasive and may be applied to data collected in the past. In this paper, we provide a discriminant function to sex great cormorants using external measurements. Males were larger than females in all linear body measurements, but there were no significant differences between adults and juveniles. Thus, data on juveniles and adults within a sex was combined. Discriminant equations with the most commonly used linear measurements, wing length and bill length, were provided. If identifying birds with discriminant function values D₂ < −1.256 as females and those with D₂ > 0.916 as males, 99% of birds will be correctly sexed. The method presented here makes it possible to account for sex-specific patterns in ecological studies of the great cormorant and may be applied to data collected in the past. The cross-application of discriminant functions developed for other populations of the great cormorant produces a 5.4% and 7.5% misclassification rate for birds from northern Poland using discriminant equations developed for populations in Greece and the Netherlands, respectively.

The Harderian and lacrimal glands are the main orbital glands of the avian lacrimal apparatus and contribute to the tear film, nictitating membrane function, and local protection of the ocular surface. Although the ocular adnexa have been well described in domestic birds, the morphology and function of these organs remain poorly characterized in free-living species. This study aimed to characterize the morphology and histochemistry of these glands in the Great Spotted Woodpecker. The material consisted of 18 individuals found dead in the natural environment in Poland. Gross anatomical, morphometric, histological, and histochemical analyses were performed. Both glands occupied typical orbital positions. The secretory units of the Harderian gland consisted of one predominant epithelial cell type, contrasting with the more heterogeneous epithelial organization reported in some other avian species. Both glands were compound tubuloacinar structures. The Harderian gland opened into the lower conjunctival sac, whereas the smaller lacrimal gland drained into the dorsal conjunctival sac. The Harderian gland had a more homogeneous secretory parenchyma and a well-developed excretory duct system. The overall morphology of both glands was comparable to that described in other birds. However, the histochemical secretory profile differed from that reported in several species: the Harderian gland produced mainly acidic mucosubstances, whereas the lacrimal gland showed a mixed secretory profile. The immune component of both glands had a diffuse and periductal distribution, which contrasted with the pattern described in some birds. These findings show that the Harderian and lacrimal glands are structurally and histochemically distinct and suggest complementary roles in ocular surface maintenance in this species. At the same time, the results indicate selected morphological and functional differences compared with both domestic and other free-living birds.