I had never heard of the Midway canaries until I read Rosemary Low’s article in Cage & Aviary Birds (1). Midway is an atoll comprising two small islands in the middle of the Pacific ocean, but is widely known thanks to the name it gave to one of the pivotal naval battles of the Second World War (2). It is not the sort of place you would expect to find canaries living in the wild, but that is where they have made their home, over 8,000 miles from the Canary Islands. How did they get there?
The abridged story is that a total of 11 domestic canaries, were released there in 1910 (3). They quickly became established and the population has since fluctuated from approximately 1000 in 1923, down to 30 in 1945 after the introduction of rats to the island, and to over 3000 in 1999 after the rats had been exterminated.
It is a curious article. It brings together various strands of the atoll’s history, mostly of a ‘human interest’ nature (nothing wrong with that), but ignores some of the major events. For example, the author tells us about President Roosevelt sending 21 marines to deter Japanese poachers, but doesn’t mention the Battle of Midway – the equivalent of a tourist guide to Normandy telling us stories about smugglers but ignoring the D-Day landings. It is the same when she chronicles the history of the Midway canaries. The story comes over well, but the birds themselves hold little interest for her. Rosemary Low is well known as an authority on parrots and other psittacines, and worked at two bird parks on the Canary Islands. You might expect some personal observations on the wild canaries she saw while she was there, instead she recalls the feeding habits of lorikeets.
For anyone interested in canaries, the article falls short. It fails to recognise that the canaries of Midway Island are a living experiment: what happens when a closed population of domesticated birds is released into the wild? Conventional wisdom decrees that yellow canaries are unfit to survive without man’s protection and would revert to the wild type (assuming that they survived at all). Did that happen, and if so, how long did it take? Are there any traces of domestication (e.g. variegated specimens) left? Unfortunately, the article does not even ask the questions, let alone provide answers. I decided to find out.
The first question to address is how did the birds on Midway manage to survive when similar experiments on other islands (e.g. the south eastern Hawaiian islands, and on Skokholm island off the coast of Pembrokeshire) have failed (4). The lack of indigenous predators is a major factor. According to Avibase, 159 bird species have been recorded on Midway, but all the potential predators (ospreys, black kite etc) are rare/accidental visitors (5). It also helps that, contrary to first impressions, man has continued to intervene. Midway Island has been designated a National Wildlife Refuge since 1988 and many of the measures taken to protect the native bird population (e.g. the extermination of rats) have also benefitted the canaries.
The next question is how have the canaries changed over the last century? My starting point was The Birds of the Hawaiian Islands (6), a source that Rosemary Low evidently used, even though it is not mentioned in the article. It is a stunning revelation: contrary to everything that I had expected, it appears that the Midway canaries remain predominantly clear yellow birds!
‘Midway birds are comprised largely of the pale yellow variety, although occasional genetic throwbacks with streaks are also reported, and bleaching has resulted in reports in summer of nearly white birds’.
The last known introduction of domesticated canaries into the local population was of six birds released in 1976 (7); you would expect any reversionary tendencies to have become apparent by now. We know that the original pair was described as ‘yellow canaries (called by us Canton canaries)’, presumably clears, but possibly variegated specimens (8). Rather than become darker, the reverse appears to have occurred: they are almost all clear birds now.
I wasn’t expecting that. Everything we know about natural selection would predict a population of predominantly green birds after more than a century in the wild, but it simply hasn’t happened. Three potential reasons spring to mind: firstly, the absence of natural predators may have nullified the benefit of camouflaged plumage; secondly, the clear yellow plumage may act as a signal of the ‘fitness’ of a potential mate and make them more attractive than dark rivals; thirdly, there may be climatic benefits. Clear feathers don’t absorb heat as much as dark plumage, and in a climate whose coldest point of the year is 17°C (9), that could be significant.
Does this have a bearing on the fine spangled sort? I think it does. It tells us that in a closed population, with no natural predators or other environmental constraints, the clear phenotype is self-sustaining. It demonstrates how a mutation (it could just as easily be the spangled gene) could be maintained and improved two hundred years before the science of genetics was established. The key to success was not genetic expertise, but simply keeping the mutation isolated.
- The canaries of Midway by Rosemary Low, Cage & Aviary Birds, 27 July 2016. p.15.
- The Battle of Midway was a naval battle between the USA and Japan. It was engaged six months after the destruction of Pearl Harbour, and swung the war of the Pacific in the USA’s favour.
- The Introduction and Acclimatization of Yellow Canaries on Midway Island by William Alanson Bryan, The Auk, Vol XXIX (1922) p.339. https://sora.unm.edu/sites/default/files/journals/auk/v029n03/p0339-p0342.pdf There is confusion about the actual number of birds released. In this account there were ten youngsters and two imported males. There is an implication that the mother was also released, but this is not clear.
- The Cinnamon Bird, by R. M. Lockley, 1948. An account of releasing domesticated canaries on the island of Skokholm, off the Pembrokeshire coast. After a promising start (including a mule produced from a migrating goldfinch), the birds were wiped out by sparrow hawks.
- The Birds of the Hawaiian Islands: Occurrence, History, Distribution, and Status by R.L. & L. Pyle, (2009). Courtesy of B.P. Bishop Museum, Honolulu, HI, U.S.A. Version 1 (31 December 2009).
- The Introduction and Acclimatization of Yellow Canaries on Midway Island, p.340.