Developmental impairment in eurasian dipper nestlings exposed to urban stream pollutants

Abstract

Avian studies of endocrine disruption traditionally have focused on reproductive impairment, given that many environmental contaminants affect sex steroid hormones. There is also increasing interest in altered thyroid function, and associated early development, particularly in altricial species with extended developmental windows. Both types of effect are relevant under the complex pollutant conditions created in streams draining urban areas, but case studies are scarce. Therefore, the authors measured breeding performance, as well as nestling growth, condition, and plasma thyroid hormones, in 87 Eurasian dipper (Cinclus cinclus) nests on 36 urban and rural streams in south and mid-Wales (UK); invertebrate prey data were also collected. The objective of the present study was to evaluate whether urban stream pollution or food scarcity might affect reproduction or development in this specialized aquatic songbird. Clutch sizes and egg fertility were similar on rural and urban streams, whereas nest success was actually higher at urban sites and food abundance was not significantly reduced. However, subtle but important differences were apparent. Urban nestlings were significantly lighter than rural nestlings for their body size (condition index), and brood sex ratios were increasingly male biased with increasing urbanization. The nestling thyroid hormone profile closely reflected urban land use, whereas depressed triiodothyronine (T3) hormones and poorer body condition were associated with higher exposure to polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs) at urbanized sites. These data suggest that PCBs, PBDEs, and/or accompanying contaminants in urban streams could be affecting dipper nestling development, with potential consequences for the birds' fitness.

Sex‐specific changes in thyroid gland function and circulating thyroid hormones in nestling American kestrels (Falco sparverius) following embryonic exposure to polybrominated diphenyl ethers by maternal transfer

“…The findings of the present study support and develop our understanding of the effects of PBDEs on thyroid hormones in young birds . In the present study, the controlled exposure of kestrels to PBDEs in a laboratory setting allowed for identification of thyroidal effects that can be attributed to PBDEs in relative isolation, without the confounding influence of exposure to multiple thyroid hormone–disrupting compounds (e.g., polychlorinated biphenyls) experienced by wild birds (e.g., Morrissey et al ). We found that embryonic exposure by maternal transfer to the technical PBDE mixture DE‐71 altered thyroid gland function and circulating thyroid hormones in female, but not male, kestrel nestlings during the period of rapid growth.…”

A review of urban impacts on avian life‐history evolution: Does city living lead to slower pace of life?

“…Six comparisons report only results on first clutches, and four comparisons include both first and second clutches. In these studies (Mennechez & Clergeau, ; Minias, ; Morrissey et al., ; and Newhouse et al., ) no differences in the probability of laying a second clutch is reported between urban and rural populations, and trends along the urbanization gradient are similar for first and second clutches. In addition, Bailly et al.…”

Diseases of wild birds in southern Rio Grande do Sul, Brazil

“…Furthermore, some authors have observed that the high concentration of organochlorines (OGC) in tissues of northern Baltic Sea nestlings seagulls found dead can enhance the septicemia risk (Hario et al 2004). OGCs decrease the ability of the immune system to respond correctly to infections (Hario et al 2004, Morrissey et al 2014. It should be emphasized that the southernmost region of RS, where most of those birds of this work came from, is a well-developed agricultural region with large rice and soybeans crops.…”