This week’s #BeakoftheWeek nomination is a honeycreeper, and you don’t find many more impressive beak adaptations than in these guys.
The fantastically named i’iwi, pronounced ‘ee-EE-vee’, or scarlett hawaiian honeycreeper (if you don’t want to get pulled up for saying it incorrectly), is endemic to the Hawaiian islands. Its distinctive bright plumage and decurved bill make it an impressive sight to behold. It is about 15cm long, with males being slightly heavier than their female counterparts. They come from the finch family fringilidae and are part of the subfamily carduelinae.
The Hawaiian honeycreepers are held up as a great example of adaptive radiation, being less famous, but more diverse than Darwin’s finches. In this illustration you can see the massive variation in beak size and shape that exists amongst this group, allowing them to fill different niches on the island chain. Here is a bit more on this topic.
This I’iwi is a good demonstration of coevolution, with their decurved bill being adapted to extract nectar from the flowers of lobeloid plants (Campanulaceae). These flowers are a perfect fit for their bill. Check out this video to see one feeding, and for a bit more information about them. The precise fit of their beaks allows the plants to make use of these birds as pollinators, all in exchange for some delicious nectar. Although they are primarily major fans of nectar, they have been known to partake in some invertebrate ingestion.
The Hawaiian islands are the most isolated island archipelago in the world. How on earth did the Hawaiian honeycreepers’ progenitors get there? There are many theories as to how these birds ended up on these islands in the first place and this video from untamedscience.com takes a light hearted look at them.
This species typically lays 2 eggs, which are then incubated from around 14 days by the female alone. Both parents take part in feeding the chicks, although the female is seen to do most of the work. The I’iwi is renowned for its long flights in search of the flowers of the ohi’a tree (Metrosideros polymorpha) and these long flights are thought to be the reason behind them being one of only three honeycreeper species that occur on more than one island.
Their beautiful plumage is hard to miss and historically, native pre-european Hawaiians, made capes from this species feathers which were used as symbols of prestige and power. Some of their scarlett feathers can be seen in the cape below.
Unfortunately ‘I’ iwi is in decline, and is described as vulnerable on the IUCN redlist, and like with other Hawaiian honeycreepers, the pesky mosquito and avian malaria is the root cause of this. With a mortality rate of around 90% from one infected mosquito bite, and little sign of resistance building up, it is a worrying time to be an I’iwi. Coupled to this there is a threat posed by the introduced mammals such as cats and rats.
There is thought to have been over 50 different species of Hawaiian honeycreeper at one stage, and there is now thought to only be about 20 left, with some of these presumed to be extinct also. The latest extinction came as recently as 2004 with the last po’ouli (Melamprosops phaeosoma) dying in captivity. There may be some hope though. Recent studies on the Hawai’i ‘Amakihi (Hemignathus virens virens) show that they are found in areas where avian malaria is active, possibly demonstrating some sort of resistance. Conservation efforts concentrating on habitat restoration and disease control are ongoing, and protected areas have been set up in their native highland forests.
BirdLife International 2012. Vestiaria coccinea. The IUCN Red List of Threatened Species. Version 2014.3. <www.iucnredlist.org>. Downloaded on 29 May 2015.
BirdLife International (2015) Species factsheet: Vestiaria coccinea. Downloaded from http://www.birdlife.org on 28/05/2015.
Fancy, Steven G. and C. John Ralph. 1998. Iiwi (Vestiaria coccinea), The Birds of North America Online (A. Poole, Ed.). Ithaca: Cornell Lab of Ornithology; Retrieved from the Birds of North America Online: http://bna.birds.cornell.edu/bna/species/327
Pratt, D. (2010). Iiwi (Drepanis coccinea). In: del Hoyo, J., Elliott, A., Sargatal, J., Christie, D.A. & de Juana, E. (eds.) (2014). Handbook of the Birds of the World Alive. Lynx Edicions, Barcelona. (retrieved from http://www.hbw.com/node/61452 on 28 May 2015).
Images & Videos
“‘Ahu ‘ula (feather cape)” by Hiart is licensed under Creative Commons CC0 1.0 Universal Public Domain Dedication
The Nature Conservancy. 2011. Hawaiian ‘I’iwi bird. [Online]. [01/06/2015]. Available from: https://www.youtube.com/watch?v=nZyuqS-Kb7k