Figure 1. Key to the maps
In contrast to this book’s first edition, the facing-page treatments that accompany each painted color plate are more comprehensive and include range maps. This format allows the user to quickly identify the bird in question without, in most cases, having to refer to the species accounts within the main body of the book. Thus, the facing-plate accounts are abridged yet self-contained accounts of each species. For an explanation of the maps, please see Figure 1.
Figure 1. Key to the maps
The expanded species accounts in the body of the book are the main reference and provide more detailed information, including other widely used names, more detailed description consisting of identification aids (including length in centimeters, field marks, and special behavioral or distributional clues), subspecies, similar species, voice, habitat, habits (including nesting data), range, and taxonomy (when relevant).
Measurements. The length measurement is for comparative purposes. It is not intended for in-the-hand species identification, as different populations and sexes oft en show substantial size variation, and our measurements are from study skins, not living birds. Measurements were derived primarily from Rand and Gilliard (1967), the latest and most comprehensive source of measurements for New Guinea birds. In some cases, these were replaced by measurements from HANZAB for birds originating in Australia, or from other updated sources, or from measurements we made ourselves. For a few species, additional measurements are given to aid comparisons. Wing length is the standard measurement of the folded wing, as measured from the carpal bend of the wing to the tip of the wing, with the wing flattened against the ruler (more properly termed wing arc). For seabirds and raptors (hawks, eagles, and kin), wingspan (distance between the tips of the fully extended wings) measurements were taken from Harrison (1983) and Fergusson-Lees and Christie (2001), respectively, but be aware that min-max values may show too wide a range of values for some species whose geographic distributions extend beyond NG.
Status. Each species account opens with a brief statement on the species’ status in the New Guinea Region—residency, migratory pattern, abundance, and main habitats. Generally, five categories of abundance are used, listed here from most to least numerous: abundant, common, uncommon, rare, and vagrant. An abundant species is seen daily in good numbers in the right habitat, whereas a vagrant species is known from only 1–5 records in the whole NG Region and its distribution does not normally include the region. Most migrants are either Palearctic migrants (from northern Eurasia) or AU migrants (Australian). Hypothetical species reported from the region are of uncertain status and lack adequate documentation. The types of bird habitats are explained on page 21.
Description. The descriptions present points for identification and plumage differences useful for ageing and sexing birds. Key field marks are italicized. For names of the parts of a bird and its plumage, please see Figure 2. Once a year, birds gradually shed all their feathers and replace them with new ones, a process termed molt. During molt, the plumage coloration may change, and related species oft en follow similar sequential patterns. Descriptive information on plumage development in New Guinea birds has been derived mainly by study of museum specimens and from field data, when available.
The plumage categories are as follows:
All Plumages—adult and juvenile indistinguishable.
Adult—sexes indistinguishable as adults; may be indicated as breeding or nonbreeding, if either apply.
Morphs (phases)—in cases of more than one type of normal adult plumage (most species have only a single morph), e.g., Variable Goshawk.
Male and/or Female—adult birds distinguishable by sex.
Imm—(immature) a distinct plumage after the juvenile plumage and before the adult plumage.
Juv—(juvenile) the first plumage following the downy plumage of a hatched chick.
Natal—downy chick.
Figure 2. Parts of a bird
Subspecies. Only subspecies that are obvious or easily discernible are listed. Thinly separated or clinal (varying) subspecies are pooled and identified as a group. If the differences among all the subspecies are obscure, they are described as minor. If a species also lives outside the New Guinea Region, its subspecies in the region is named, and the relationship to other extraregional subspecies is identified as endemic or shared. If the species does not have subspecies (is monotypic), then the subspecies status is omitted. The format for the Subspecies Section is thus:
Subspp. (the number of subspecies, in number of groups): name of a subspecies or group (its geographical range) and key identifying features.
Similar species. This section provides the means to distinguish the focal species from similar-appearing birds.
Voice. Includes songs and calls, when available. These are carried across from the previous edition and modified and/or supplemented by other sources and our unpublished observations (especially those of contributor Jared Diamond). We have extensively compared these descriptions against recordings available at the websites for both xeno-canto Australasia and Cornell Laboratory of Ornithology’s Macaulay Library. Collaborators have sent us additional recordings.
Habits. This section details habitat and behavior, including social system, foraging, diet, and nesting. In cases where the bird is better known from somewhere else, usually Australia, then the information is referenced as “AU data” or a similar equivalent for another region.
Range. Describes the known geographic and elevational distribution of the species, including geographic distribution outside the New Guinea Region. We first state whether the species is endemic, that is, whether found only in the NG Region. Next is given a list of islands where the species occurs in the region. The species’ distribution on the island of NG follows. Elevational distributions are in meters, with the primary elevations of occurrence presented, often followed by marginal occurrences in parentheses. Finally, if the species exists outside the region, that distribution is given.
Taxonomy. Recent or potential changes in classification are given here.
Extralimital spp. These are species living just beyond the New Guinea Region that might be expected to turn up in the region. This category especially pertains to look-alike species (e.g., Black-shouldered Kite and Little Eagle).