‘Death is a part of life; extinction is quite another thing, it is the end of birth.’
China: Between Clouds and Dreams – by Phil Agland, produced by River Films.
Martha the Passenger Pigeon is famous for all the wrong reasons. She should have been an anonymous bird among billions, but she became the last living soul of her species. She died alone in Cincinnati zoo in 1914.
It must have been clear to all and sundry that the species was about to disappear long before Martha’s demise, many birds have been kept in captivity for thousands of years and so the techniques to breed birds in captivity were, even then, well known. And despite there being three colonies in captivity it never occurred to anyone to use these skills to save the species from extinction, the mind-set was not concerned with conserving or preserving species in those days; a tragic failure on humanity’s part.
Now things are very different. I wish that by that I meant that we are taking greater care of our environment and species are not in danger of extinction, sadly that is not the case, there are probably more bird species today facing that fate-worse-than-death than ever before. What is different now though is that we are at least thinking about how we can prevent such things from happening.
One prevention method is captive breeding. This method is expensive and not always effective, but it could be the last chance of a species if all else has failed.
If the existence of a species in the wild looks untenable, we can take some of those birds into captivity with a view not just to keeping them alive as long as possible, but trying to give them the conditions they need to breed; thus perpetuating the species. A species becomes extinct when it can no longer produce enough recruits to replace those that are dying. Keeping free-living, wild birds safe and preventing them from being killed or dying early is of course the aim, but when that doesn’t happen then we have to step in and find another way. That other way is to establish breeding populations in captivity; this means that –
- The species still exists if the wild population fails
- There is a pool of birds from which recruits from the wild population can be selected to:
- Boost current populations (example Black Stilt)
- Reintroduce species to suitable habitat (example Shore Plover)
- It buys time if habitat is unsuitable to repair the environment for later reintroduction (example California Condor)
- It may provide the opportunity for genetic mixing in discrete populations (example Philippines Eagle)
- A species bred in captivity can be released into a different habitat into which wild populations are reluctant to spread (example Mauritius Kestrel).
- Captive bred populations can provide information for scientific research with a view to conserving the species (example New Zealand Dotterel – now Northern and Southern Red-breasted Plover).
There are of course negatives to be considered in captive breeding –
- The numbers of individuals needed for a viable population can make housing and caring for them complicated and expensive. This may determine the numbers involved. If the numbers are too low this makes the population unviable due to inbreeding or simply a restricted choice of mate.
- The birds’ behaviour may be affected by captivity, thus if birds are to be released they may not have the ability to survive due to altered;
- predator avoidance
- foraging patterns
- sleep patterns
- activity levels
- social interaction with others of the species
Captive breeding is not the silver bullet, it is not the answer to preventing population declines, it is however a safety net that can make the difference between a species existing or not.
Captive breeding differs from headstarting in that the whole reproduction process occurs in captivity. The adults are captive, the eggs are laid and hatched in captivity and the young remain in captivity unless they are selected to be recruits to a wild population.
Among waders there are many examples of this method of preservation of a species.
Most recently there has been the, as yet unsuccessful, Spoon-billed Sandpiper captive breeding programme, quite why these birds have not bred is not known, every effort has been made to maximise their chances.
There is also the Black Stilt, known as Kakī in New Zealand. This has been captive bred for many years and although many releases are made each year the population has grown only very slowly.
Another captive bred species from New Zealand if the Shore Plover. This bird’s range shrank to just one island in the Chatham Island group, Rangatira. Birds were selected and taken into captivity for breeding. The progeny of these captive birds have been released onto predator free islands with a view to establishing new colonies. The danger of having all your eggs in one basket are well known, so distinct and separate colonies are the way to prevent an extinction caused by a disastrous weather of pollution event wiping out all the remaining birds.
Non wader species are also dealt with in the same way. Famously there is one species that is extinct in the wild but lives on in captivity at the moment and that is Spix’s Macaw from Brazil which is kept in various locations around the world, but principally in the middle east.
Reintroductions can also occur from captive populations, one example of this is the California Condor which became extinct in the wild but the young of captive birds are released into the wild establishing a breeding population.
Some reintroductions replace birds in new, and different, locations to those of a small remaining population. The reason for doing this is the eggs in basket syndrome. An example of that is the shore plover or, for a non-wader species, red kite in the UK.
Rick Simpson – Wader Quest
With thanks to the following photographers: Tim Evanson
CC denotes images are subject to CC license