Gross pathology of herons and egrets (family Ardeidae) at a wildlife rehabilitation centre in Northern California


  • Molly Horgan School of Veterinary Medicine, University of California-Davis, Davis, CA, USA
  • Rebecca Duerr International Bird Rescue, Fairfield, CA, USA



Ardeids, egret, Eustrongylides, gout, heron, meloxicam, metabolic bone disease, NSAID, necropsy, pathology, renal failure, vitamin D, wildlife rehabilitation


Gross necropsies were performed on all herons and egrets (family Ardeidae) that died or were euthanized at a wildlife rehabilitation centre in Fairfield, California, over a six-week period in the summer of 2018 (n = 145). Of the animals necropsied, 108 (74.5%) were euthanized and 37 (25.5%) died. Common reasons for euthanasia were trauma (n = 24), MBD (n = 39) and non-specific signs such as hypothermia and obtundation that persisted in the face of medical and supportive care (n = 32). MBD was found both in birds at admission (n = 9) and later in care (n = 34), despite calcium supplementation to correct calcium:phosphorus ratios of foods. Feeder fish were suspected to be deficient in vitamin D, and supplementation successfully reduced the development of this problem during the care later in the season. Nematodes of the genus Eustrongylides were found in the coelomic cavities of 43 (30%) birds. High burdens were often accompanied by coelomitis and abscessation involving internal organs. Visceral gout (n = 10) and intestinal perforation (n = 4) were both strongly associated with the administration of meloxicam. These findings suggest meloxicam should be used with caution in these species. Other less common findings included septic arthritis, intestinal perforation and hepatomegaly. This study describes common gross pathological findings of herons and egrets in a wildlife rehabilitation centre in California and demonstrates the utility of gross necropsies in determining cause of death when more advanced post-mortem diagnostics are unavailable


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Carpenter J.W. & Marion C.J., editors. 2018. Carpenter’s exotic animal formulary, 5th edition. St. Louis, MO: Elsevier.

Coker S.M., Hernandez S.M., Kistler W.M., Curry S.E., Welch C.N., Barron H.W., Harsch S., Murray M.H. & Yabsley M.J. 2017. Diversity and prevalence of hemoparasites of wading birds in Southern Florida, USA. International Journal for Parasitology: Parasites and Wildlife 6(3), 220–225. doi: 10.1016/j.ijppaw.2017.08.003.

Cuthbert R., Parry–Jones J., Green R.E. & Pain D.J. 2007. NSAIDs and scavenging birds: potential impacts beyond Asia’s critically endangered vultures. Biology Letters 3, 90–93. doi: 10.1098/rsbl.2006.0554.

Deardorff T.L., Karch N.J. & Holm S.E. 2008. Dioxin levels in ash and soil generated in Southern California fires. Organohalogen Compounds 70, 2284–2288.

De Matos R. 2008. Calcium metabolism in birds. Veterinary Clinics of North America: Exotic Animal Practice 11, 59–82. doi: 10.1016/j.cvex.2007.09.005.

Dijkstra B., Guzman D.S., Gustavsen K., Owens S.D., Hass C., Kass P.H. & Paul-Murphy J.R. 2015. Renal, gastrointestinal, and hemostatic effects of oral administration of meloxicam to Hispaniolan Amazon parrots (Amazona ventralis). American Journal of Veterinary Research 76(4), 308–317. doi: 10.2460/ajvr.76.4.308.

Dyer F., Diesel G., Cooles S. & Tait A. 2010. Suspected adverse reactions, 2009. Veterinary Record 167, 118–121. doi: 10.1136/vr.c3650.

Enberg T.B., Braun L.D. & Kuzma A.B. 2006. Gastrointestinal perforation in five dogs associated with the administration of meloxicam. Journal of Veterinary Emergency and Critical Care 16(1), 34–43.

Engelhardt G. 1996. Pharmacology of meloxicam, a new non-steroidal anti–inflammatory drug with an improved safety profile through preferential inhibition of COX-2. British Journal of Rheumatology 35(1), 4–12. doi: 10.1093/rheumatology/35.suppl_1.4.

Franson C. & Custer T.W. 1994. Eustrongylidiasis in wading birds from colonies in California, Texas, and Rhode Island, USA. Colonial Waterbirds 17(2), 168–172. doi: 10.2307/1521295.

Griggs T., Lee J.C., Park H., Singhvi A., Wallace T., Ward J. & Watkins D. 2017. Northern California fires have destroyed at least 5,700 buildings. The New York Times [Internet news service]. Accessed on the internet at on 5 January 2019

Hoopes L. & Clauss T. 2016. Investigation of a potential vitamin D3 deficiency in an African penguin (Spheniscus demersus) collection [abstract]. In International Association for Aquatic Medicine (IAAAM) Conference Proceedings 2016, May 21–26. Virginia Beach, VA. Accessed on the internet at on 5 January 2019

Horgan M., Duerr R.S. & Murphy B. 2021. Clinical and pathologic findings of an outbreak of vitamin D -responsive 3 metabolic bone disease in heron and egret (family ardeidae) chicks fed capelin (mallotus villosus). Journal of Zoo and Wildlife Medicine 51(4), 958–969. doi: 10.1638/2019-0238.

Madrone Audubon Society. West 9th Street Heronry [monograph on the internet]. Accessed on the internet at on 5 January 2019

Malesa-Ciecwierz M. & Usydus Z. 2015. Vitamin D: can fish food–based solutions be used for reduction of vitamin D deficiency in Poland? Nutrition 31(1), 187–92. doi: 10.1016/j.nut.2014.07.003.

Meteyer C.U., Rideout B.A., Gilbert M., Shivaprasad H.L. & Oaks J.L. 2005. Pathology and proposed pathophysiology of diclofenac poisoning in free–living and experimentally exposed oriental white–backed vultures (Gyps bengalensis). Journal of Wildlife Diseases 41(4), 707–716. doi: 10.7589/0090-3558-41.4.707.

Montesinos A., Ardiaca M., Juan-Sallés C. & Tesouro M.A. 2015. Effects of meloxicam on hematologic and plasma biochemical analyte values and results of histologic examination of kidney biopsy specimens of African Grey Parrots (Psittacus erithacus). Journal of Avian Medicine and Surgery 29(1), 1–5. doi: 10.1647/2013-056.

Naidoo V. & Swan G.E. 2009. Diclofenac toxicity in Gyps vulture is associated with decreased uric acid excretion and not renal portal vasoconstriction. Comparative Biochemistry and Physiology. Part C 149, 269–274. doi: 10.1016/j.cbpc.2008.07.014.

Oaks J.L., Gilbert M., Virani M.Z., Watson R.T., Meteyer C.U., Rideout B.A., Shivaprasad H.L., Ahmed S., Chaudhry M.J., Arshad M., Mahmood S., Ali A. & Khan A.A. 2004. Diclofenac residues as the cause of vulture population decline in Pakistan. Nature 427, 630–633. doi: 10.1038/nature02317.

Phalen D.N., Drew M.L., Contreras C., Roset K. & Mora M. 2005. Naturally occurring secondary nutritional hyperparathyroidism in Cattle Egrets (Bubulcus ibis) from Central Texas. Journal of Wildlife Diseases 41, 401–415. doi: 10.7589/0090-3558-41.2.401.

Santos C.S., Brandão R., Monteiro M.S., Bastos A.C., Soares A.M. & Loureiro S. 2017. Assessment of DNA damage in Ardea cinerea and Ciconia ciconia: a five-year study in Portuguese birds retrieved for rehabilitation. Ecotoxicology and Environmental Safety 136, 104–110. doi: 10.1016/j.ecoenv.2016.10.039.

Sinclair K.M., Church M.E., Farver T.B., Lowenstine L.J., Owens S.D. & Paul-Murphy J. 2012. Effects of meloxicam on hematologic and plasma biochemical analysis variables and results of histologic examination of tissue specimens of Japanese Quail (Coturnix japonica). American Journal of Veterinary Research 73(11), 1720–1727. doi: 10.2460/ajvr.73.11.1720.

Slifka K., Crissey S.D., Khan S., Moser A., Chen T.C., Mathieu J. & Holick M.F. 2001. Nutritional status in captive Bottlenose Dolphins (Tursiops truncates). In M. Edwardset al. (eds.): Proceedings of the fourth conference on zoo and wildlife nutrition. Pp. 151–157. Lake Buena Vista, FL: AZA Nutrition Advisory Group.

Spalding M.G., Bancroft G.T. & Forrester D.J. 1993. The epizootiology of Eustrongylidosis in wading birds (Ciconiiformes) in Florida. Journal of Wildlife Diseases 29(2), 237–249. doi: 10.7589/0090-3558-29.2.237.

Spalding M.G. & Forrester D.J. 1993. Pathogenesis of Eustrongylides ignotus (Nematoda: Dioctophymatoidea) in Ciconiiformes. Journal of Wildlife Diseases 29(2), 250–260. doi: 10.7589/0090-3558-29.2.250.

Summa N.M., Guzman D.S., Larrat S., Troncy E., Bird D.M., Lair S. & Fitzgerald G. 2017. Evaluation of high dosages of oral meloxicam in American Kestrels (Falco sparverius). Journal of Avian Medicine and Surgery 31(2), 108–116. doi: 10.1647/2015-150.

Thompson H.M., Fernandes A., Rose M., White S. & Blackburn A. 2006. Possible chemical causes of skeletal deformities in Grey Heron Nestlings (Ardea cinerea) in North Nottinghamshire, UK. Chemosphere 65, 400–409. doi: 10.1016/j.chemosphere.2006.02.007.

Van Franeker J.A. 2004. Save the North Sea Fulmar–litter–EcoQO manual part 1: collection and dissection procedures. Wageningen, Netherlands: Alterra. Accessed on the internet at on 27 December 2018

Wallace J.L. 2001. Pathogenesis of NSAID-induced gastroduodenal mucosal injury. Best Practice & Research Clinical Gastroenterology 15(5), 691–703. doi: 10.1053/bega.2001.0229.

Wiese J.H., Davidson W.R. & Nettles V.F. 1977. Large scale mortality of nestling ardeids caused by nematode infection. Journal of Wildlife Diseases 13(4), 376–382. doi: 10.7589/0090-3558-13.4.376.

Ziegler A.F., Welte S.C., Miller E.A. & Nolan T.J. 2000. Eustrongylidiasis in eastern great blue herons (Ardea herodias). Avian Diseases 44, 443–448. doi: 10.2307/1592560.



How to Cite

Horgan, M., & Duerr, R. (2021). Gross pathology of herons and egrets (family Ardeidae) at a wildlife rehabilitation centre in Northern California. Wildlife Rehabilitation Bulletin, 37(1), 29–41.



Original Articles