Birds of paradise, biogeography and ecology in New Guinea: a review
Birds of paradise, biogeography and ecology in New Guinea: a review
Birds of paradise, biogeography and ecology in New Guinea: a review
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912 M. Heads<br />
Milne Bay isl<strong>and</strong>s<br />
The isl<strong>and</strong>s <strong>of</strong> the D'Entrecasteaux <strong>and</strong> Louisiade Archipelagos<br />
form an eastward extension <strong>of</strong> the <strong>New</strong> Gu<strong>in</strong>ea orogen<br />
possibly related to the Owen Stanley terrane (Pigram &<br />
Davies, 1987) <strong>and</strong> the D'Entrecasteaux isl<strong>and</strong>s <strong>in</strong>clude active<br />
metamorphic core complexes (Tregon<strong>in</strong>g et al., 1998). The<br />
low Trobri<strong>and</strong> Isl<strong>and</strong>s to the north also lie with<strong>in</strong> the belt.<br />
<strong>Birds</strong> <strong>of</strong> <strong>paradise</strong> are represented <strong>in</strong> this region only by three<br />
species <strong>of</strong> Manucodia. M. keraudrenii hunste<strong>in</strong>i is endemic<br />
to the three D'Entrecasteaux isl<strong>and</strong>s. M. comrii Sclater is<br />
known only from these same isl<strong>and</strong>s (M. c. comrii) <strong>and</strong>, at<br />
the family's limit, the Trobri<strong>and</strong> Isl<strong>and</strong>s (M. c. trobri<strong>and</strong>i<br />
Mayr); there is a spread<strong>in</strong>g centre <strong>in</strong> the Woodlark Bas<strong>in</strong><br />
(de Boer & Duffels, 1996a; Tregon<strong>in</strong>g et al., 1998) <strong>and</strong> these<br />
ranges may have been split apart by the open<strong>in</strong>g <strong>of</strong> the bas<strong>in</strong>.<br />
F<strong>in</strong>ally, M. atra Lesson has an endemic race, M. a. altera<br />
Rothschild <strong>and</strong> Hartert, on Sudest ( ˆ Tagula) I. <strong>in</strong> the<br />
Louisiades, but is not present on the D'Entrecasteaux or<br />
Trobri<strong>and</strong> Isl<strong>and</strong>s.<br />
It is strik<strong>in</strong>g that the only isl<strong>and</strong>s <strong>of</strong>f <strong>New</strong> Gu<strong>in</strong>ea that<br />
birds <strong>of</strong> <strong>paradise</strong> occur on ± northern Moluccas, Western<br />
Papuan Isl<strong>and</strong>s, Japen, D'Entrecasteaux, Trobri<strong>and</strong>s, <strong>and</strong><br />
Sudest ± all lie with<strong>in</strong> the <strong>New</strong> Gu<strong>in</strong>ea orogen (Fig. 2). The<br />
isl<strong>and</strong>s <strong>of</strong> Manam, Karkar <strong>and</strong> the Bismarck Archipelago lie<br />
outside this belt <strong>and</strong> do not have birds <strong>of</strong> <strong>paradise</strong>. A very<br />
similar distribution on the ma<strong>in</strong>l<strong>and</strong> <strong>and</strong> the Milne Bay<br />
Isl<strong>and</strong>s, but absent from the Bismarck Archipelago, is seen <strong>in</strong><br />
the snake Tropidonophis aenigmaticus Malnate (Fig. 38).<br />
Restricted isl<strong>and</strong> endemics, such as Semioptera <strong>and</strong><br />
Lycocorax on the Moluccas <strong>and</strong> Manucodia atra altera on<br />
Sudest, are usually assumed to have been derived from a<br />
widespread population on the ma<strong>in</strong>l<strong>and</strong>. However, the<br />
isl<strong>and</strong> endemics may once have had a much more extensive<br />
distribution on now-sunken l<strong>and</strong>, for example around<br />
Sudest, which is `obviously submerged' (LoÈ f¯er, 1977). In<br />
this case birds that are currently `ma<strong>in</strong>l<strong>and</strong>' <strong>and</strong> `isl<strong>and</strong>'<br />
forms are probably descendants <strong>of</strong> a common ancestor<br />
formerly widespread over very different Mesozoic <strong>and</strong><br />
Tertiary geography. Likewise, areas <strong>of</strong> ocean ¯oor <strong>in</strong> the<br />
Gulf <strong>of</strong> Papua, such as the Eastern Fields Fan (50,000 km 2 )<br />
between Port Moresby <strong>and</strong> the northern end <strong>of</strong> the Great<br />
Barrier Reef, have been subsid<strong>in</strong>g ever s<strong>in</strong>ce the Coral Sea<br />
began rift<strong>in</strong>g open <strong>in</strong> the Miocene (Mutter, 1975). This<br />
could expla<strong>in</strong> biogeographical connections between the<br />
trans-Fly <strong>and</strong> Port Moresby regions `cutt<strong>in</strong>g the corner'<br />
across the Gulf <strong>of</strong> Papua, seen for example <strong>in</strong> several snakes<br />
mapped by O'Shea (1996).<br />
The isl<strong>and</strong> taxa cited above <strong>in</strong>clude dist<strong>in</strong>ctive endemic<br />
genera, as well as barely differentiated taxa, but the same<br />
pr<strong>in</strong>ciple may apply. M<strong>in</strong>or morphological <strong>and</strong> molecular<br />
differences may re¯ect ancient but rapid <strong>and</strong> m<strong>in</strong>or evolutionary<br />
divergence followed by a long periods <strong>of</strong> stasis, with<br />
possible geographical convergence <strong>of</strong> populations on converg<strong>in</strong>g<br />
terranes.<br />
R<strong>and</strong> & Gilliard (1967) cited many species, for example <strong>in</strong><br />
Eos (Fig. 15), which `favour' small isl<strong>and</strong>s. But perhaps these<br />
taxa have no choice if small islets form the only l<strong>and</strong> currently<br />
available <strong>in</strong> their respective regions. The islets may represent<br />
the last l<strong>and</strong> <strong>in</strong> an area <strong>of</strong> subsidence, <strong>and</strong> competition from<br />
related forms prevents establishment <strong>in</strong> neighbour<strong>in</strong>g territory.<br />
These birds survive on small islets <strong>and</strong> atolls because,<br />
®rstly, they were already <strong>in</strong> the region <strong>in</strong> a prior geography,<br />
<strong>and</strong> secondly, because they either possessed the necessary preadaptations<br />
for this <strong>ecology</strong> or were able to adapt. The vast<br />
majority <strong>of</strong> small islet taxa around <strong>New</strong> Gu<strong>in</strong>ea are not found<br />
on all the many islets available, but only those <strong>in</strong> particular<br />
regions. This implies that someth<strong>in</strong>g other than the small islet<br />
<strong>ecology</strong> is determ<strong>in</strong><strong>in</strong>g the distribution.<br />
Northern limits <strong>of</strong> birds <strong>of</strong> <strong>paradise</strong> <strong>and</strong> bowerbirds<br />
Despite be<strong>in</strong>g on the western Papuan Isl<strong>and</strong>s <strong>and</strong> the Milne<br />
Bay isl<strong>and</strong>s, no birds <strong>of</strong> <strong>paradise</strong> or bowerbirds are known<br />
from the <strong>of</strong>fshore isl<strong>and</strong>s <strong>of</strong> Biak, Karkar, Manam, <strong>New</strong><br />
Brita<strong>in</strong>, or <strong>New</strong> Irel<strong>and</strong>, all <strong>of</strong> which provide suitable habitat:<br />
hills with closed ra<strong>in</strong>forest. The isl<strong>and</strong> <strong>of</strong> Karkar, for example<br />
(Fig. 4), is 25 km across <strong>and</strong> 1850 m high, largely covered <strong>in</strong><br />
ra<strong>in</strong>forest <strong>and</strong> only 15 km <strong>of</strong>fshore. Yet there has never been<br />
a s<strong>in</strong>gle record <strong>of</strong> a bird <strong>of</strong> <strong>paradise</strong> or bowerbird there. <strong>New</strong><br />
Brita<strong>in</strong> is a much larger isl<strong>and</strong>, 90 km <strong>of</strong>f <strong>New</strong> Gu<strong>in</strong>ea. A<br />
surpris<strong>in</strong>g 70% <strong>of</strong> the species on the part <strong>of</strong> <strong>New</strong> Gu<strong>in</strong>ea<br />
opposite <strong>New</strong> Brita<strong>in</strong> are not represented on <strong>New</strong> Brita<strong>in</strong><br />
(Mayr, 1940). Gressitt (1982b) frankly admitted that the<br />
absence <strong>of</strong> many <strong>New</strong> Gu<strong>in</strong>ea groups from the Bismarck<br />
Archipelago, `<strong>in</strong> spite <strong>of</strong> proximity <strong>and</strong> isl<strong>and</strong> stepp<strong>in</strong>gstones',<br />
is `puzzl<strong>in</strong>g'. In fact the avifauna <strong>of</strong> these isl<strong>and</strong>s is<br />
both rich (Coates, 1990) <strong>and</strong> quite different from that on the<br />
ma<strong>in</strong>l<strong>and</strong> ± many ¯oristic <strong>and</strong> faunistic works (e.g. R<strong>and</strong> &<br />
Gilliard, 1967; Beehler et al., 1986) are logically limited to<br />
the ma<strong>in</strong>l<strong>and</strong> taxa. Because the <strong>of</strong>fshore isl<strong>and</strong>s are so close it<br />
seems that `dispersal' <strong>in</strong> the sense <strong>of</strong> physical movement, or <strong>in</strong><br />
this case lack <strong>of</strong> dispersal, has noth<strong>in</strong>g to do with the major<br />
faunistic difference. On the other h<strong>and</strong>, it is surely not a<br />
co<strong>in</strong>cidence that the northern boundary <strong>of</strong> the <strong>New</strong> Gu<strong>in</strong>ea<br />
orogen runs along the north coast <strong>and</strong> marks the mutual<br />
boundary <strong>of</strong> the two faunas, <strong>in</strong>clud<strong>in</strong>g the northern limit <strong>of</strong><br />
Paradisaeidae <strong>and</strong> Ptilonorhynchidae.<br />
The dist<strong>in</strong>ctive fauna <strong>of</strong> Karkar <strong>and</strong> the other fr<strong>in</strong>g<strong>in</strong>g<br />
isl<strong>and</strong>s <strong>in</strong>cludes birds such as Charmosyna rubrigularis<br />
(Sclater), Macropygia mack<strong>in</strong>layi (Ramsay), Cacomantis<br />
variolasus fortior (Rothschild & Hartert), Ducula pistr<strong>in</strong>aria<br />
Bonaparte, Monarcha c<strong>in</strong>erascens Temm<strong>in</strong>ck <strong>and</strong> Myzomela<br />
sclateri Forbes (maps <strong>in</strong> Coates, 1990). These are all on<br />
Karkar <strong>and</strong> several <strong>of</strong> the other northern isl<strong>and</strong>s (<strong>New</strong><br />
Brita<strong>in</strong>, etc.) but are not on the <strong>New</strong> Gu<strong>in</strong>ea ma<strong>in</strong>l<strong>and</strong>,<br />
where they are replaced by allied forms. At subspecies level<br />
Gallicolumba b. beccarii (Salvadori) is <strong>in</strong> the mounta<strong>in</strong>s<br />
throughout <strong>New</strong> Gu<strong>in</strong>ea, <strong>and</strong> G. b. johannae (Sclater) is on<br />
Karkar Isl<strong>and</strong> <strong>and</strong> the Bismarck Archipelago. Megapodius<br />
freyc<strong>in</strong>et (Gaimard) shows the boundary well, with<br />
M. f. af®nis Meyer <strong>in</strong> northern <strong>New</strong> Gu<strong>in</strong>ea <strong>and</strong> M. f.<br />
eremita Hartlaub on Manus, Long Isl<strong>and</strong>, Siassi (ˆ Umboi<br />
or Rooke) Isl<strong>and</strong>, <strong>New</strong> Brita<strong>in</strong>, <strong>and</strong> the Solomon Isl<strong>and</strong>s.<br />
Karkar Isl<strong>and</strong>, on the biogeographical boundary between the<br />
two, has a `mixed population' (R<strong>and</strong> & Gilliard, 1967).<br />
Ó Blackwell Science Ltd 2001, Journal <strong>of</strong> Biogeography, 28, 893±925