This is the last of my
instalments based on Tring’s non-passerine birds. These are some of the rarest
bird species in the world and there are many commonalities to their endangerment but conservationists are working tirelessly to bring
them back from the brink and success is increasing.
Nene – Branta sandvicensis
I am quite familiar with the nene
as a small, friendly goose who doesn’t bite your hand like those pesky
greylags. I refer to childhood visits to WWT Slimbridge where my sister and I
would spend hours feeding grain to the cosmopolitan waterfowl assemblages,
inevitably running out of seed half way around the park.
The nēnē, or Hawaiian goose, is
common in Slimbridge but on its native Hawaiian islands it became very rare. Up
until colonial settlement of the islands, nene were relatively common, the
equivalent of Canada geese in North America, but man was responsible for a
severe decline via hunting and predation by introduced mongoose, pigs and cats.
From Captain James Cook’s arrival in 1778 the population decreased from c.
25,000 to just 30 in 1952. Thankfully, in stepped Sir Peter Scott of WWT fame
who spearheaded a captive breeding program to save the nene. Luckily these
geese breed well in captivity and so the program and introductions have been
successful with the population up to 2,500. Next time I feed a nene I will
think of their story and remember the important role we must play in conserving
our birds.
Christmas frigatebird – Fregata andrewsi
The Christmas frigatebird is the
rarest of the five frigatebird species in the family Fregatidae and it only
breeds on Christmas Island in the Indian Ocean. In the grander scheme of things,
frigatebirds are most closely related to cormorants (Phalacrocoracidae) and
boobies (Sulidae) and sit in the order Suliformes which has been separated from
its pelecaniform cousins.
I always get a sense of awe when
I see a frigatebird, not because it’s especially big, impressive or beautiful
but because they have a pterosaurian appearance, their angular black wings and
tapering tail hanging motionless on the wind. The appearance of ease which they
give to flight is not merely an illusion but a reflection of their
super-pneumatic bones which comprise just 5% of their weight. This, coupled
with the largest wingspan-to-body-weight ratio, means that frigatebirds can
spend ages floating on the air, flapping infrequently and expending little
energy. Like swifts, they can even over-night on the wing.
Frigatebirds nest in large
colonies where males vie for females using huge, inflated gular sacs which are
bright red in colour. From above, the females encircle groups of males who
point skywards to reveal their pouches, vibrating their bills to produce a
drumming sound. Regular readers will not be surprised to see the presence of sexual
selection again, especially the colour red which is usually a sign of a healthy
diet rich in carotenoids. Furthermore, frigatebirds are unusual amongst
seabirds for having blood-borne parasites. Parasites are important in handicap
theory whereby only males with the best immune systems can stave off infection
and produce their bright colouration.
Parasitised though they may be,
frigatebirds are famous for turning parasite themselves. Kleptoparasitism is
the act of stealing food from others and frigatebirds are consummate bullies
who terrorise the smaller boobies, tropicbirds and gulls, forcing them to give
up their catch or the contents of their stomachs. Perhaps piratebird would be a
more fitting moniker.
Philippine eagle – Pithecophaga jefferyi
Another critically endangered
bird, the Philippine eagle is the largest eagle in terms of length and wing
area. It is endemic to the Philippines where deforestation has drastically
limited its range and population. It evolved to be the apex predator with
little competition on the islands and has such it has grown to a huge size with
a fearsome set of talons and a monstrous beak which can make short work of
their prey. Their prey is pretty much any terrestrial vertebrate short of
humans or larger ungulates. They get the name Pithecophaga for their taste in monkeys (the Philippine long-tailed
macaque) but flying foxes, squirrels, giant cloud rats, civets, snakes,
lizards, owls, hornbills and even deer also make up this eagles diet. We are
used to images of eagles soaring overhead but Philippine eagles are jungle
denizens, appearing out of nowhere to seize their prey from branches. For such
a large bird they are surprisingly stealthy.
Saint Lucia Parrot – Amazona versicolor
The Amazona parrots are a speciose genus and members in mainland
Central and South America can be widespread and common however the few species
strung out across the Caribbean tend to be rare. Amazons have low dispersal
ability so they are often range restricted and on the islands of the West
Indies each species tends to be endemic to just one or two islands. The
Caribbean islands have seen a lot of development and habitat loss and this has
pushed many endemics closer to extinction and the Saint Lucia parrot is no exception.
It declined from around 1,000 individuals to just 150 birds towards the end of
the 1970’s. Since then, and with great public support, this parrot has bounced
back.
Of these various island-endemic
Amazons, I chose to write about the Saint Lucia parrot as I hope to see it in
the wild this summer. I am going to Saint Lucia for two weeks and I hope to
take in as much of the islands natural history as possible. Saint Lucia has at
least four endemic bird species including a warbler (Setophaga delicata), an oriole (Icterus
laudabilis) and a black finch (Melanospiza
richardsoni) as well as rare reptiles, stunning rainforest and rich coral
reef. I cannot wait!
Keel-billed motmot – Electron carinatum
Motmots are stunning birds
characterised by their bright colours and long tails which often end in
racket-like tips. Unsurprisingly their tails play a role in courtship but one
intriguing use seems to be as an anti-pursuit deterrent. According to studies
conducted on turquoise-browed motmots (Eumomota
superciliosa), motmots wag their tails when they notice a potential
predator. The signal says ‘I have seen you and I will fly away so don’t even
bother’. This signal benefits both parties as neither wastes its energy in a
fruitless pursuit.
During my time in Honduras in
2011 we caught a blue-crowned motmot (Momotus
momota) in a mist net and one thing that stood out was the impressive bill
which is used to grasp lizards and insects. To catch their prey motmots perch silently
then pounce from above. Confined to the New World, the Momotidae occupy a niche
similar to the Old World forest kingfishers (Halcyonidae) which share their
order. In June I return to Honduras and will hopefully see more of these
beautiful birds and maybe even the keel-billed motmot itself.
Guam rail – Gallirallus owstoni
The genus Gallirallus caused some issue when first we passed it in our avian
tour as few of the species seemed to be in the collection. Resolution of this
issue also lead to multiple explanations for their initial absence. The first
was that many of the rail species had only recently joined this genus having
traditionally been placed in other genera such as Rallus. Another explanation was the fact that this genus comprises
many extremely rare species which had been placed safely in more secure
collections.
Ancestors of the Gallirallus rails managed to populate
many of the islands across Australasia and the Pacific whereupon they became
flightless in the absence of terrestrial predators. Latter introductions of
mammals such as cats and rats have put many rail species at risk and even
eliminated some. The Tongatapu rail (G.
hypoleucus), Dieffenbach’s rail (G.
dieffenbachii), Wake Island rail (G.
wakensis) and Tahiti rail (G.
pacificus) have all gone extinct since the late 18th century
with the New Caledonian rail (G.
lafresnayanus) probably extinct. The Okinawa rail (G. okinawae) and Calayan rail (G.
calayanus) were only discovered in 1981 and 2004, respectively,
demonstrating the cryptic nature of these species.
The Guam rail is a typical member
of the genus being a flightless, island endemic. However it is extinct in the wild
having been extirpated from Guam in the 1980’s as a result of the introduced
brown tree snake. It exists only in captivity where a breeding program hopes to
establish a future population. It is a shame that this American territory
should lose this species as well as other endemics but the might of American
conservation is now behind the Guam rail. 17 zoos are participating in a
captive breeding program with around 120 individuals alive in captivity. Eradication
of rats and snakes is the key to the success of reintroduction programs such as
this and the reintroductions of Guam rails to a 22 hectare enclosure and an
isolated atoll have proved successful so there is hope for the future of this
species.
Eagle eyed observers might have
noticed that the Guam rail is taxonomically out of sync with the rest of the
species this week. That is because it was the last species that I measured in
Tring. After exhaustively searching for every last species the museum had to
offer, chasing up loose ends and find the most elusive specimens, I finished the
job after six months measuring. Together, with my friends and colleagues Nico
and Sam, we measured 3,046 species from 11,490 skins taking 103,410 measurements.
It was a staggering effort, an intellectual journey and thoroughly enjoyable
experience. My blog was a vehicle for exploring some of the amazing birds covered
in that period (all 90 pictured below!) so do go back and explore my past posts yourself. As for the
future, adventure beckons with trips to Honduras and Saint Lucia followed,
hopefully, by further avian experiences and I’ll be birding all the way!
