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 ===== Introduction ===== ===== Introduction =====
  
-Whilst doing a bit of research around this contentious topic, it became quickly apparent that there is no study or paper to find, which conclusively proves that feeding bread to waterfowl is the sole cause for the development of angel wing deformities. Despite this fact, most wildlife and waterfowl experts seem to agree that the overwhelming cause of angel wing is an unhealthily high protein and / or carbohydrate based diet. Unsurprisingly, it was not difficult to find plenty of advice and warnings suggesting not to feed bread to birds, and in particular not to waterfowl. However, with all the advice being provided, no scientific references were given, which would certainly help to clarify and understand the situation.+{{ :swan.jpeg?200|}}Whilst doing a bit of research around this contentious topic, it became quickly apparent that there is no study or paper to find, which conclusively proves that feeding bread to waterfowl is the sole cause for the development of angel wing deformities. Despite this fact, most wildlife and waterfowl experts seem to agree that the overwhelming cause of angel wing is an unhealthily high protein and / or carbohydrate based diet. Unsurprisingly, it was not difficult to find plenty of advice and warnings suggesting not to feed bread to birds, and in particular not to waterfowl. However, with all the advice being provided, no scientific references were given, which would certainly help to clarify and understand the situation.
  
 On the other hand, we did find a variety of research, which has been undertaken with the aim to establish possible causes for angel wing deformities. Most of the available literature has been produced by using and abusing domestic birds raised for human food production, or by doing questionable feeding trials with captive raised wild bird species. However, we didn’t find any useful research, which has been undertaken to establish the causes for angel wing deformities at the source, meaning in the wild. In this context, please note that the list of research reviewed and used for this blog post is not meant to be exhaustive. On the other hand, we did find a variety of research, which has been undertaken with the aim to establish possible causes for angel wing deformities. Most of the available literature has been produced by using and abusing domestic birds raised for human food production, or by doing questionable feeding trials with captive raised wild bird species. However, we didn’t find any useful research, which has been undertaken to establish the causes for angel wing deformities at the source, meaning in the wild. In this context, please note that the list of research reviewed and used for this blog post is not meant to be exhaustive.
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 The most common factors cited to contribute to the development of angel wing deformities are excessively fast growth in relatively slow growing temperate and tropical species. Overfeeding, both with a too high protein and too high energy diet is thought to be important. A relative vitamin E deficiency has also been suggested as being relevant. Canada geese fed on high protein levels (20%) developed this condition more frequently than those fed lower protein diets.((Kreeger, T.J. & Walser, M.M., Carpometacarpal deformity in giant Canada geese (Branta canadensis maxima Delacour), 1984, volume 20, pages 245-248)) The most common factors cited to contribute to the development of angel wing deformities are excessively fast growth in relatively slow growing temperate and tropical species. Overfeeding, both with a too high protein and too high energy diet is thought to be important. A relative vitamin E deficiency has also been suggested as being relevant. Canada geese fed on high protein levels (20%) developed this condition more frequently than those fed lower protein diets.((Kreeger, T.J. & Walser, M.M., Carpometacarpal deformity in giant Canada geese (Branta canadensis maxima Delacour), 1984, volume 20, pages 245-248))
    
-Incorrect incubation conditions and hatching problems have also been suggested as possible causes. Angel wing has been reported more commonly in geese and swans than in ducks. The possibility of genetic predisposition has also been considered. Domestic breeds, which have been bred for rapid weight gain, appear more susceptible. Males may be more affected than females. The reason for the disproportionate occurrence affecting the left wing is unknown. ((Kreeger, T.J. & Walser, M.M., Carpometacarpal deformity in giant Canada geese (Branta canadensis maxima Delacour), 1984, volume 20, pages 245-248.)) ((Zoological Society of London, London, UK, Kear, J., Notes on the nutrition of young waterfowl, with special reference to slipped-wing, 1973, volume 13, pages 97-100)) ((Yeisley, C.L., Surgical correction of valgus carpal deformities in waterfowl, Proceedings of the Association of Avian Veterinarians, 1993, pages 161-163))  +Incorrect incubation conditions and hatching problems have also been suggested as possible causes. Angel wing has been reported more commonly in geese and swans than in ducks. The possibility of genetic predisposition has also been considered. Domestic breeds, which have been bred for rapid weight gain, appear more susceptible. Males may be more affected than females. The reason for the disproportionate occurrence affecting the left wing is unknown. ((Kreeger, T.J. & Walser, M.M., Carpometacarpal deformity in giant Canada geese (Branta canadensis maxima Delacour), 1984, volume 20, pages 245-248)) ((Zoological Society of London, London, UK, Kear, J., Notes on the nutrition of young waterfowl, with special reference to slipped-wing, 1973, volume 13, pages 97-100)) ((Yeisley, C.L., Surgical correction of valgus carpal deformities in waterfowl, Proceedings of the Association of Avian Veterinarians, 1993, pages 161-163))  
  
 Kear reported that angel wing deformities in wild geese are affected by several factors, including lack of exercise, large flock size, improper feeding, rearing under heat stress because of high ambient temperatures, feeling frightened frequently and improper management.((Zoological Society of London, London, UK, Kear, J., Notes on the nutrition of young waterfowl, with special reference to slipped-wing, 1973, volume 13, pages 97-100))  Kear reported that angel wing deformities in wild geese are affected by several factors, including lack of exercise, large flock size, improper feeding, rearing under heat stress because of high ambient temperatures, feeling frightened frequently and improper management.((Zoological Society of London, London, UK, Kear, J., Notes on the nutrition of young waterfowl, with special reference to slipped-wing, 1973, volume 13, pages 97-100)) 
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 Angel wing deformities have been found in wild and captive trumpeter swan, Canada goose, swan goose, Hawaiian goose, Andean goose, Magellan goose, blue-winged goose, Egyptian goose, Indian spotbill, New Zealand grey duck, Pacific black duck, African yellow-bill, chestnut-breasted teal, crested duck, red-crested pochard, mountain duck and wild-type muscovy ducks, mute swan, Cape Barren goose, mallards, black swan, Pacific black duck and Australian shoveler. However, angel wing deformities have also been found in Northern goshawk, black stilt, grey heron, bustard and masked boobies. ((Bilateral Valgus Deformity of the Distal Wings (Angel Wing) in a Northern Goshawk (Accipiter gentilis), Petra Zsivanovits, Deborah J. Monks, and Neil A. Forbes, Journal of Avian Medicine and Surgery 2006 20 (1), 21-26)) ((L. Pitman, Robert & Ballance, Lisa & Bost, Charles. (2012). Incidence of Wing Deformities (‘Angel Wing’) Among Masked Boobies at Clipperton Island: Life History Consequences and Insight into Etiology. The Wilson Journal of Ornithology. 124. 597-602. 10.2307/23324568))  Angel wing deformities have been found in wild and captive trumpeter swan, Canada goose, swan goose, Hawaiian goose, Andean goose, Magellan goose, blue-winged goose, Egyptian goose, Indian spotbill, New Zealand grey duck, Pacific black duck, African yellow-bill, chestnut-breasted teal, crested duck, red-crested pochard, mountain duck and wild-type muscovy ducks, mute swan, Cape Barren goose, mallards, black swan, Pacific black duck and Australian shoveler. However, angel wing deformities have also been found in Northern goshawk, black stilt, grey heron, bustard and masked boobies. ((Bilateral Valgus Deformity of the Distal Wings (Angel Wing) in a Northern Goshawk (Accipiter gentilis), Petra Zsivanovits, Deborah J. Monks, and Neil A. Forbes, Journal of Avian Medicine and Surgery 2006 20 (1), 21-26)) ((L. Pitman, Robert & Ballance, Lisa & Bost, Charles. (2012). Incidence of Wing Deformities (‘Angel Wing’) Among Masked Boobies at Clipperton Island: Life History Consequences and Insight into Etiology. The Wilson Journal of Ornithology. 124. 597-602. 10.2307/23324568)) 
    
-Interestingly, pollution may also play an important part in the development of skeletal deformities. The levels of polychlorinated biphenyls (PCBs), polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) detected in affected heron nestlings were sufficiently high to suggest that this may be the underlying cause of the deformities, possibly due to effects on deposition of calcium in bone.+Interestingly, pollution may also play an important part in the development of skeletal deformities. The levels of polychlorinated biphenyls (PCBs), polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) detected in affected heron nestlings were sufficiently high to suggest that this may be the underlying cause of the deformities, possibly due to effects on deposition of calcium in bone. ((Helen M. Thompson, Alwyn Fernandes, Martin Rose, Shaun White, Adrian Blackburn, Possible chemical causes of skeletal deformities in grey heron nestlings (Ardea cinerea) in North Nottinghamshire, UK, Chemosphere, volume 65, Issue 3, 2006, pages 400-409))
    
 ===== Contributing Factors ===== ===== Contributing Factors =====
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 However, as with many things, there are always two sides of a story. Many people have a romanticised view of nature, and of what it means for animals to live in the wild. They believe nature is some kind of paradise, where animals live happy lives. Also, many people forget that what they know as ‘nature’ is in fact a mostly manmade landscape with fragmented and isolated habitats, which in itself is a big problem.  However, as with many things, there are always two sides of a story. Many people have a romanticised view of nature, and of what it means for animals to live in the wild. They believe nature is some kind of paradise, where animals live happy lives. Also, many people forget that what they know as ‘nature’ is in fact a mostly manmade landscape with fragmented and isolated habitats, which in itself is a big problem. 
-All our actions have an impact, be it on other humans or on non-human animals. This is also true for feeding wild animals. There are powerful reasons to care for non-human animals, as they are sentient beings, who can experience suffering as humans do. This is why we should be concerned about what happens to them. But we should also be careful and make sure that our actions do not lead to an increase of wild animal suffering.+All our actions have an impact, be it on other humans or on non-human animals. This is also true for feeding wild animals. There are powerful reasons to care for non-human animals, as they are sentient beings, who can experience suffering as humans do. This is why we should be concerned about what happens to them. But we should also be careful and make sure that our actions do not lead to an increase of wild animal suffering. ((Reed, D. H. (2004), Extinction risk in fragmented habitats. Animal Conservation, 7: 181-191. doi:10.1017/S1367943004001313))
  
 It is worth remembering that in certain situations feeding of wild birds may create dependencies, which may impact on the ability of wild birds to survive, in particular during winter. It is our responsibility to keep this in mind. Also, during prolonged periods of severe or cold weather, disturbance of wild birds should be reduced. Bird watchers, bird ringers, walkers, dog-walkers, horse-riders and water-based sports should avoid disturbing groups of feeding or resting birds. It is worth remembering that in certain situations feeding of wild birds may create dependencies, which may impact on the ability of wild birds to survive, in particular during winter. It is our responsibility to keep this in mind. Also, during prolonged periods of severe or cold weather, disturbance of wild birds should be reduced. Bird watchers, bird ringers, walkers, dog-walkers, horse-riders and water-based sports should avoid disturbing groups of feeding or resting birds.
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 Disease transmission is better facilitated under dense population conditions. Habituation of swans, geese and ducks being fed in parks potentially creates further conflict, if for example large geese or swans are defending a nesting female or a brood of goslings or cygnets. Also, supplemental feeding of migrant birds can interfere with normal migration patterns by delaying departure or suspending the behaviour altogether. Disease transmission is better facilitated under dense population conditions. Habituation of swans, geese and ducks being fed in parks potentially creates further conflict, if for example large geese or swans are defending a nesting female or a brood of goslings or cygnets. Also, supplemental feeding of migrant birds can interfere with normal migration patterns by delaying departure or suspending the behaviour altogether.
 The best solution for waterfowl problems situated around public parks is to minimise uncontrolled excessive supplemental feeding. Feeding a balanced diet will decrease the likelihood of nutritional disorders to occur. However, feeding a balanced diet will not prevent overcrowding, disease concerns, habitat degradation, habituation or the risks associated with premature breeding attempts or delayed migration. The best solution for waterfowl problems situated around public parks is to minimise uncontrolled excessive supplemental feeding. Feeding a balanced diet will decrease the likelihood of nutritional disorders to occur. However, feeding a balanced diet will not prevent overcrowding, disease concerns, habitat degradation, habituation or the risks associated with premature breeding attempts or delayed migration.
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-Bibliography 
-Kreeger, T.J. & Walser, M.M., Carpometacarpal deformity in giant Canada geese (Branta canadensis maxima Delacour), 1984, volume 20, pages 245-248  
-Kreeger, T.J. & Walser, M.M., Carpometacarpal deformity in giant Canada geese (Branta canadensis maxima Delacour), 1984, volume 20, pages 245-248.  
-Zoological Society of London, London, UK, Kear, J., Notes on the nutrition of young waterfowl, with special reference to slipped-wing, 1973, volume 13, pages 97-100  
-Yeisley, C.L., Surgical correction of valgus carpal deformities in waterfowl, Proceedings of the Association of Avian Veterinarians, 1993, pages 161-163  
-Zoological Society of London, London, UK, Kear, J., Notes on the nutrition of young waterfowl, with special reference to slipped-wing, 1973, volume 13, pages 97-100  
-T.N. Tully, M.P.C. Lawton & G.M. Dorrenstein (Eds.), Butterworth Heinemann, Oxford, UK, 2000, Cranes, Olsen, G.H., pages 215-227  
-Tully, T.N. Jr., Dorrestein, G.M., & Jones, A.K., Saunders, Elsevier Limited., 2009, Cranes, Olsen, G.H. , pages 243-257  
-Lin, M. J., Chang, S. C., Lin, T. Y., Cheng, Y. S., Lee, Y. P., & Fan, Y. K. (2015). Factors Affecting the Incidence of Angel Wing in White Roman Geese: Stocking Density and Genetic Selection. Asian-Australasian journal of animal sciences, 29(6), 901-7  
-Zoological Society of London, London, UK, Kear, J., Notes on the nutrition of young waterfowl, with special reference to slipped-wing, 1973, volume 13, pages 97-100.  
-B.W. Ritchie, G.J. Harrison & L.R. Harrison, Wingers Publishing Inc., Lake Worth, Fl., 1994, Anseriformes, Olsen, J.H., pages 1237-1275.  
-]D. Brown, ABK Publications, South Tweed Heads, NSW, Australia, 1998  
-Serafin, J.A. The influence of diet composition upon growth and development of sandhill cranes, 1982, valume 84, pages 427-434  
-Bilateral Valgus Deformity of the Distal Wings (Angel Wing) in a Northern Goshawk (Accipiter gentilis), Petra Zsivanovits, Deborah J. Monks, and Neil A. Forbes, Journal of Avian Medicine and Surgery 2006 20 (1), 21-26  
-L. Pitman, Robert & Ballance, Lisa & Bost, Charles. (2012). Incidence of Wing Deformities (‘Angel Wing’) Among Masked Boobies at Clipperton Island: Life History Consequences and Insight into Etiology. The Wilson Journal of Ornithology. 124. 597-602. 10.2307/23324568  
-Helen M. Thompson, Alwyn Fernandes, Martin Rose, Shaun White, Adrian Blackburn, Possible chemical causes of skeletal deformities in grey heron nestlings (Ardea cinerea) in North Nottinghamshire, UK, Chemosphere, volume 65, Issue 3, 2006, pages 400-409  
-Reed, D. H. (2004), Extinction risk in fragmented habitats. Animal Conservation, 7: 181-191. doi:10.1017/S1367943004001313  
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