New Guinea is famous amongst biologists for its endemism (i.e. plants and animals found nowhere else). In the case of birds, nearly one in two (456 of 943 species) is endemic; an astonishing proportion. It has also benefitted from field work from high profile zoological explorers who are famed writers such as Ernst Mayr, Tim Flannery and Jared Diamond. It is also a difficult place to travel in, and for this reason most visiting birders tend to travel on organised birding tours. My interest in New Guinea stems largely from my interest in using the large tropical islands of New Guinea (the second largest island in the world), Madagascar and Borneo as a comparative against the moderately sized island of Sri Lanka which is very rich in bio-diversity. In the public perception, New Guinea is a rainforest clad mysterious island with hundreds of primitive tribes, a lost world, where plants and animals which occur nowhere else can be found.
There is no doubting that New Guinea has a staggering number of endemic plants and animals. However, endemism at species level should not be confused with that at higher levels of taxonomic rank. From a scientific perspective, New Guinea is one of Australia’s youngest geological provinces. Dan Polhemous writing in volume 1 of ‘The Ecology of Papua’ refers to New Guinea ‘as the mountainous, tectonically deformed northern margin of Australia’. Many plants and animals at the level of families and higher levels such as orders are shared with Australia and in fact New Guinea has only existed as a discrete unit after the beginning of the current warm interglacial period of less than 20,000 years. New Guinea in the case of many species groups has only new species that are relatively new or very recent ‘branches’ in the tree of life. In comparison, the Australian continent and neighbouring areas to the east of Wallace’s line have endemic species that branched out much earlier. Thus, if one takes a molecular phylogenetic approach and asks if there are ‘long branches’ of the tree of life found in New Guinea, which are endemic, the answer may be “no”. But this ignores the fascinating and magical profusion of species (however recent in geological terms) that occur there, found nowhere else in the world.
The radiation of species in New Guinea is not merely due to a radiation of species into a physical habitat which is structurally complex. It is also due to its complex geological history. The northern part of New Guinea is believed to comprise at least 32 separate tectono-stratigraphic terranes. As the northward moving Indo-Australasian tectonic plate collides with the westward moving Pacific plate, accretion layers or terranes are formed. One can think of this as part of the tectonic plate that is slipping underneath having parts of it scraped off and deposited on the tectonic plate that is overriding it. As the surface geology changes, so do the soils and the plant life and hence the insect life. There are biological and physical changes to the environment. Whether it is a bird or a butterfly, the changes in the environment will apply section pressures. Random mutations in genes may result in plants and animals that are better suited for the changed conditions. Over millions of years, the selection pressures will result in the creation of new species. And as conditions continue to change, even more new species will form. Thus, New Guinea becomes a fascinating living laboratory in which the process of evolution can be studied.
One of the most spectacular examples of the amazing evolutionary radiation in New Guinea is in birds. Many years ago, I was quick to purchase a copy of the Birds of New Guinea by Beehler, Pratt and Zimmerman when it came out in 1986. Although there have been other bird books on New Guinea, they were not complete field guides to all of the mainland. The best field guide until recently for geographical coverage had been the second revised edition of the ‘Birds of New Guinea by Pratt and Beehler’. However, it did not cover the Bismarck Archipelago and Bougainville. In 2017, a new book by Phil Gregory addressed this shortcoming with the ‘Birds of New Guinea: Including Bismarck Archipelago and Bougainville’. As this is such an important addition to the ornithological literature, I will discuss the book in more detail.
Something strikingly different from conventional field guides is that the distribution maps are placed on the plates. On first impressions, it is a detraction from the colour plates on aesthetic grounds. Indeed, some may find it an ugly imposition. But I suspect this style may become more popular as it helps to visualise where a bird is found when you browse the plates. If a book is being bought for the artistic merits of its plates, then it is a serious detraction. When people are buying a field guide for practical use in the field, then having the distribution map next to the bird is a very useful device. Saving you the effort of having to swing your head a millimetre or two from side to side may seem a trivial saving. But the maps next to the birds do make a surprising improvement in one’s ability to process parallel streams of information.
Continues on the 2nd of February.