Ian’s Bird of the Week – Masked Booby ~ by Ian Montgomery
Newsletter – 5/20/11
We got a good view of a female Lesser Frigatebird at Lucinda on Wednesday when we did our regular wader count so I considered this species for bird of the week, forgetting that it had featured in March. So here is another spectacular seabird instead: the Masked Booby.
The first photo shows a portrait of a male bird, distinguishable from the female by its yellow bill. That of the female, second photo, has a greenish tinge to it. As you can see from these photos, Boobies are very approachable and the name comes from the Spanish ‘bobo’ meaning clown or fool as sailors found the birds easy to catch.
The difference between the sexes is subtle though the female is larger and they are easier to tell apart when seen together, like the pair in the third photo on a beach. Boobies and Gannets are very social and have sophisticated behaviours for display, territorial disputes and fishing so the ‘bobo’ label was a bit hasty.
All these photos were taken at East Diamond Islet, a remote cay on the eastern edge of the Barrier Reef in the Coral Sea Islands Territory, within Australia’s territorial boundaries but outside Queensland. This cay is typical of Masked Booby colonies, far offshore in tropical or sub-tropical waters, and the birds fish in deep water and are not normally seen close to the coast. The range of the Masked Booby is right around the globe and in Australasia there are colonies in northern Western Australia, northeastern Queensland, Lord Howe and Norfolk Islands and the New Zealand Kermadec Islands. The birds at the last three sites have black rather than yellow eyes and belong to a different race. Another race in the eastern Pacific with orange bills has recently been split off as a separate species the Nazca Booby.
Masked Boobies nest both on rocky cliffs and flat areas and the female in the fourth photo is sheltering a nestling and simultaneously expressing a verbal protest at being photographed. They usually lay two eggs, but the second is only an insurance policy and the first nestling to hatch will kill its sibling if it also hatches. Juvenile birds, fifth photo, look quite similar to the closely related Brown Booby but are distinguishable by having a complete white collar which in front forms a white rather than brown upper breast.
The sixth photo is of a male in flight and shows the black tail that distinguishes it from the white phase of the Red-footed Booby. Like all the gannets and other boobies, the Masked feeds by spectacular plunge-dives for fish, all members of the family have air sacs off the bronchi to absorb the impact – the original airbags. The Masked is the largest of the boobies (to 86cm/34in with a wing-span of 1.7m/5.5ft) and its maximum dive has been estimated at 100m/330ft though it’s smaller than the gannets. Gannets can reach 10m/33ft depth just from the dive and then swim down to 20-25m and usually take the target fish on the way back up.
Here are a couple of points from earlier postings. Last week I had an email from Brett who reported the northern race of the Eastern Yellow Robin at St George’s Basin, 200km south of Sydney and well south of the documented range to the Hunter Valley. He – firstname.lastname@example.org – would be interested to hear from others who have recorded it south of its supposed range. A month ago (Yellow White-eye) I inquired about a plant with large fruits and pink flowers. The plant in question is calotrope (Calotropis procera) – thank you to the respondents – an introduced weed, but popular with native birds such as this Red-headed Honeyeater in Broome.
The Sulidae – Gannets, Boobies Family has 10 species. The three Gannets are the Northern, Cape, and Australian. The seven Boobies are the Blue-footed and Red-footed, Peruvian, Nazca, Brown and the Masked Booby which Ian just wrote about. This family is part of the Suliformes Order which also includes the Frigatebirds, Cormorants, shags and the Anhingas, darters families.
Talking about the young one and the nest of the ground reminds me of:
If you come across a bird’s nest in any tree or on the ground, with young ones or eggs and the mother sitting on the young or on the eggs, you shall not take the mother with the young. (Deuteronomy 22:6 ESV)