Butterflies of Bristol 1: The Pale Owl Butterfly

The Owl butterflies are a group of about twenty very large South American butterflies, often seen in butterfly houses as they are spectacular and easy to raise on butterfly farms. Here at Bristol we have the Pale Owl butterfly, Caligo memnon.
The various species of Caligo belong to the gigantic and diverse family the Nymphalidae, and in particular to the very large subfamily (previously a full family) Satyrinae. As such they are most closely related to the multitude of “Brown” butterflies found in every grassland on earth, but among their closest relatives are the vivid iridescent blue (and just as large) Morpho butterflies, which we also have at Bristol. Also closely related are the somewhat smaller Opsiphanes species of North America.

Colourful, endangered - and in Bristol

The Gouldian, or Lady Gould’s, finch Erythrura gouldiae is one of the most beautiful small finches in the world. Sadly, the species is highly threatened in the wild, and the wild population is estimated at only a few thousand birds in the Northern Territories of Australia.

Until as recently as the 1980’s, Gouldian finches were still found in large numbers, but the impact of increased grazing, and probably even more important a shift in the fire management system, has resulted in a collapse of the population. Hot, late season fires over large areas deprive the birds of their favourite grass seeds, which is the staple diet. There are habitat restoration projects underway, but time is short for these birds. Small birds tend to have short lifespans, and numbers even at the remaining sites can vary considerably from year to year. An experimental release of birds in Queensland has appeared to have at least some success, with released birds breeding in the wild.

Gouldian finches are unusual birds in that they have three colour morph’s, the Red-, Yellow- and Black-headed forms. These are correlated with different behaviour patterns and feeding and breeding strategies as follows:

Red-headed: These birds dominate at feeders in captivity, and appear to displace other morph’s at nest sites. They are often polygamous, which together suggests they should form the majority, but in fact they are much less common than the black-headed morph. It appears they are more susceptible to stress, and have higher mortality as a result.

Black-headed: These are subordinate to Red-headed birds but dominate Yellow-heads. They have a monogamous breeding strategy, and form the bulk of the wild population

Yellow-headed: These are at the bottom of the pecking order, and are very rare in the wild. In captivity they appear the most curious, and are usually the first to locate new food sources.

Gouldian finches nest in holes, laying a small clutch of eggs and raising young on unripe seeds and insects. Another cause of their decline is a lack of nesting sites –they avoid burnt trees even if they have suitable holes in them.

As with many Australian finches, the Gouldian finch has been domesticated, and is now kept all over the world. Members of Severn Counties Foreign & British Bird Society, to which I belong, breed well into double figures every year, and they are now not especially hard to breed. If you wish to seem them therefore, you do not need to visit Australia. SCF&BBS has our Open Show this Saturday 24th October (open to the public from 2.30), so if you are interested in these birds or aviculture in general please drop by. The show is at the Methodist church hall, Down road, Winterbourne, Bristol BS36 1BN. See our website for more details.

Finally, here are some other birds that members keep and will be exhibiting at the show:

October Research Colloqium - the importance of lighting

Wednesdays colloquium was a very interesting presentation from Rowena Killick BVM&S MSc (Wild Animal Health) MRCVS, who is the RCVS Trust senior clinical training scholar in zoo and exotic medicine and surgery here at Bristol Zoo Gardens, on a research project she carried out on the Vitamin D levels of some of the new world primates and lemurs here at Bristol.

Vitamin D is synthesised in the skin when it is exposed to UV light of the correct wavelengths from precursors in the diet, and then circulates in the blood to the kidneys where it is converted into the hormone 1,25-dihydroxyvitamin D3, which is a hormone that is involved in the regulation of calcium metabolism. There is a chemically related form called Vitamin D2, which does not have such a potent effect.

The primates of Central and South America (platyrrhines) have an odd biochemical quirk compared to those of the Old World. Their internal organs are resistant to the effects of Vitamin D3, and they cannot use Vitamin D2 at all. In order to maintain proper calcium metabolism, they have circulating blood levels of D3 which are ten to one hundred times higher than similar monkeys in Africa or Asia. Living as they do close to the equator, producing sufficient active D3 is of course no problem in their home range.

The potential problem we have is that Bristol is at mid latitudes in the northern hemisphere, whereas the two groups of primates mentioned earlier all live close to the equator. In humans, lack of exposure to sufficient ultraviolet light causes serious health problems such as rickets, and even sub-clinical levels of vitamin D deficiency can result in problems with fertility, disease resistance, or even potentially cancer. Our primates all have access to outside enclosures year round, so the question is, is this sufficient?

This past year as part of routine health checks the blood vitamin D3 levels of lemurs and new world primates were measured. Although levels of Vitamin D3 were within normal ranges for published data (in fact the lemurs were at the high end), the NWP’s were at the low end, especially in winter, and there was some indication of lower bone density than would be ideal.

So, what does this mean for the husbandry of New World Primates? At present, most zoo primates are given a primate pellet which has supplementary D3 added, as well as a variety of fruit and vegetables. At Jersey metabolic bone disease in Pied Tamarins was cured by providing UVB lighting, and indications are that this kind of lighting should become standard for New World Primates without access to tropical, or at least sub-tropical, sunlight in outdoor enclosures. This would be better than providing additional dietary supplements, as the risk of overdosing would be much lower – like most vitamins, excess Vitamin D is potentially seriously toxic.

The other requirement is of course more research. The various primates of the Americas are enormously diverse, and may have requirements for more or less D3 depending on the species. For example, the nocturnal Owl Monkeys or Dourocoulis, Aotus, have apparently no higher D3 levels than Old World primates. On the other hand, some South American species like the Uakaris are notoriously difficult to breed in zoos – could a higher Vitamin D/UVB requirement be the cause?

(Image from Wikipedia)

Land of the Dodo 16: Latest news

I will draw this series on the wildlife of Mauritius with some news from the Mauritian Wildlife Foundation, taken from their annual report and latest newsletter. Check out their website – and make a donation!

The MWF Solitude Endemic Nursery in Rodrigues produced 70,000 seedlings of 50 endemic species in 2008. These included 8 seedlings of Ramosmania rodriguesii, which was down to only a single remaining wild plant until cuttings were successfully propagated.

The Mauritius Fody has been downgraded from Critically Endangered to Endangered, as a result of the successful establishment of a population on Isle Aux Aigrettes. The mainland population now stands at 130 pairs, plus another 80 on isle Aux Aigrettes. Reintroduction to Round Island is planned for the near future.

Pink Pigeons exceeded 400 wild birds for the first time in February this year. Once the population reaches 600 the population can be downgraded from Endangered to Vulnerable status.

The recent nesting season for Echo Parakeets was very successful, with 112 young fledging; the population is estimated to exceed 400 birds.

There has appeared to be a decline in the population of Mauritius Kestrel, with a reduction in the smaller population on the east coast. The total population is around 600 birds.

Rodrigues Fody was reduced to only 6 pairs in 1968, but by 2007 had increased to 3,000 individuals,

Rodrigues Warbler was reduced to 17 individuals by 1982, but had increased to 1,000 by 2007.

After numerous nesting attempts, the first Mauritius Olive White-Eye from the introduced population on isle Aux Aigrettes fledged in October 2008.



















The translocation of Telfair’s skinks to Isle Aux Aigrettes has proved a success. Not only has the skink bred outside of Round Island for the first time in 150 years, but several introduced pests such as House Shrews, Indian Wolf Snakes and FRICAN Land Snails have declined or died out altogether.

Aldabra Giant Tortoises and Radiated Tortoises were released on Round Island in 2007 as part of a PhD project to determine whether they can replace the extinct native tortoises.

Having recovered from a low of 100 individuals in the 1970’s, the population of Rodrigues Fruit bat now stands at over 5,000.

Finally, a captive breeding programme has been established on Jersey in the DWCT Herpetology department, with the aim of producing enough Lesser Night Geckos, Nactus coindemerensis, for an introduction to Ile Marianne.

PS - Reminder

The research colloquium at Bristol Zoo Education department is this Wednesday 7th October at 5.30. The subject is an investigation of Vitamin D levels in tropical primates at Bristol, and will hopefully provide useful information on the husbandry of these animals at high latitudes - is their enough sunlight for exposure outside to meet their requirements? The speaker is Rowena Killick (RCVS Trust Senior Clinical Training Scholar in Zoo Animal Medicine).

Land of the Dodo 15:Seabirds

When the Mascarenes were first discovered, the main islands did not have an extensive diversity of breeding seabirds, but offshore islets had some colonies of many species. These were often raided for eggs and young birds for food, and the burrow-nesting petrels are highly vulnerable to rats, which together have resulted in local extinctions of some species. A few of these have re-colonised naturally, but some others have been lost and world populations are now so low that it is unlikely that new colonies will be formed on the islands without outside help.

Currently only visitors to the islands are Greater and Lesser Frigate birds Fregatta sp., of which at least one species was reported as breeding when the islands were first discovered, Great Crested Terns Thallasseus bergii, and various Indian ocean gulls and terns, plus some Palaearctic migrant waders making stopovers, such as Ruddy Turnstones. Pelicans were reported offshore in 1598, probably Pink-backed Pelicans Pelecanus rufescens (which we have here at Bristol), which formerly bred in the Amirantes atolls north of Madagascar.

Three species of boobies formerly bred in the Mascarenes. One species just holds on, the Masked Booby Sula dactylatra, which breeds on Serpent Island. Red-footed Boobies Sula sula bred on Rodrigues until the 1870’s. The most important species however was the tree-nesting Abbott’s Booby, Papasula abottii (shown at top) which was probably both persecuted for food and also lost nesting habitat to deforestation. Abbott’s booby was ever only found on four stations, but today only a single breeding colony on Christmas Island remains, and this is too far away and too small to provide potential recolonists.

Several species of terns are found in the Mascarenes, some of which have recolonised after becoming locally extinct. The commonest are the Brown and Lesser Noddy, with Rodrigues also having colonies of Roseate Tern, Sooty, and Fairy Terns.






Two species of Tropicbird can be found on the islands, the inshore White-tailed Tropicbird and the more oceanic Red-Tailed Tropicbird, with the latter being the more common. They are increasing under protection and also benefiting from the recovery of the vegetation on Round Island and other seabird islets now that goats and rabbits have been removed.



The most important of the seabirds on the islands however are the various species of petrels. Petrels mostly breed in burrows, mostly only coming ashore after dark, so they are very hard to study. The Reunion Black Petrel Pseudobulweria aterrima appears to be a very rare breeder, and the breeding site was only recently located. Only once reported prior to the 19th century, it was probably always rare. It is part of a group of species which are otherwise found in the Pacific except for an extinct species from St Helena in the Atlantic. By contrast, the Wedge-Tailed and Tropical Shearwaters Puffinus sp. are both still fairly common, although Tropical Shearwater is extinct on Mauritius.

With the recovery of the vegetation in recent years, the situation on Round Island has become complex. Originally only a single species, the Round Island Petrel, believed to be a local form of the Trinidade Petrel Pterodroma arminjoniana, was known, but in recent years two other species have colonised, Bulwer’s Petrel Bulweria bulwerii, and Kermadec Petrel Pterodroma neglecta. The Kermadec Petrels sometimes hybridise with the Round Island Petrels, and it appears that a hybrid swarm of mixed parentage is forming. Both the Kermadec and Bulwers’ petrels appear to be new colonists of the western Indian Ocean.

This situation however is not unknown amongst seabirds, and sometimes islands are colonised from considerable distances away. One such colonisation probably resulted in the Reunion nesting Barau’s Petrel Pterodroma baraui. This appears to have been derived, however unlikely this seems, from the Hawaiian Petrel. Even more unlikely, these colonists seem to have brought with them on their feathers the seeds of a specialised shrub, Acacia koa, which itself has evolved into the Reunion endemic species Acacia heterophylla. On both Hawaii and Reunion the petrels and the acacia are closely associated, living at high altitudes on the slopes of the volcano.

Until recently, seabird conservation in the Mascarenes has involved only protection from persecution and habitat restoration, but attempts are just starting on direct reintroduction. One might wonder how this can be done, since seabirds all leave the breeding sites after fledging, usually for several years, but the secret is to take advantage of the tendency of fledglings to imprint on their birthplace, which in the case of petrels is whatever they see when first leaving the darkness of the burrow. In addition, many seabirds do not have post-fledging care – the chick, which at the point of fledging has a large amount of fat stored, makes its own way to the sea and teaches itself to fish. Currently being attempted are translocations of such fledglings to Isle Aux Aigrettes, with the hope that such birds will return to nest in later years. If these prove successful, possibly even Abbott’s Booby may be reintroduced at some time.

Images from Wikipedia from top:

Abotts Booby
Brown Noddy
White-Tailed Tropicbird
Wedge-Tailed Shearwater