Native forest birds in unprecedented trouble: researchers

Jan 19, 2012

Native birds at Hakalau Forest National Wildlife Refuge are in unprecedented trouble, according to a paper recently published in the journal PLoS ONE. The paper, titled "Changes in timing, duration, and symmetry of molt of Hawaiian forest birds," was authored by University of Hawai'i at Mānoa Zoology Professor Leonard Freed and Cell and Molecular Biology Professor Rebecca Cann.

In the paper, Freed and Cann report that birds are now so food-deprived that they take up to twice as long replace their feathers, an annual process known as molt. The authors confirmed the hypothesis that Japanese white-eye (Zosterops japonicus) birds are effectively competing with most species of . Their research found that both young and adult birds took longer to complete their molt. Young birds normally complete their juvenile molt in five months, beginning before June and ending in October. Now it is taking the birds as late as March of the following year to finish that molt. Adults are also taking that much longer to replace their feathers. Freed and Cann propose that this change in molt matches those in studies that experimentally starve birds.

In addition, the authors report that more adults are beginning their molt early, during months when they normally breed. Some molting females even had active brood patches. Birds generally avoid this overlap in their life history because both activities require extra energy. In their study, Freed and Cann have identified that the endangered Hawai'i creeper had the greatest molting changes. The record change for an individual bird, a Hawai'i amakihi, was set by an individual that finished its juvenile molt from the previous year in March only to begin its adult molt in May. All Hawaiian honeycreepers had significant changes.

Usually birds molt the same primary flight feathers on the two wings at the same time to maintain maneuverability. However, by 2002, all species had asymmetric molt of these feathers. This is the first time asymmetric molt has been documented throughout a community of birds. This molt was experimentally seen previously in food-limited birds. In laboratory situations, starvation of birds to 60% of normal diet leads to the changes in molt that Freed and Cann observed in nature. Native birds died at a greater rate during the months of extended molt during 2000-2004, and survival worsened each year. A control set of years in the 1990's, with fewer white-eyes, showed no trend in survival.

The authors reported that the changes in molt were associated in every detail with the increase in Japanese white-eye birds, a bird intentionally introduced to Hawai'i in 1929 to control insects. According to Freed and Cann, the molt study complements a previous 2009 Current Biology paper by the authors showing that all species of native have stunted growth and lower survival. The authors suggest that no section of the refuge is safe from the competitive effects of this introduced bird, especially the lower closed forest section of the refuge which had the greatest non-normal molt in 2006.

Explore further: Fish found in suspected tsunami debris boat quarantined

More information: To view the research paper, visit: dx.plos.org/10.1371/journal.pone.0029834

Related Stories

What limits the size of birds?

Jun 16, 2009

Why aren't birds larger? Fifteen-kilogram swans hold the current upper size record for flying birds, although the extinct Argentavis of the Miocene Epoch in Argentina is estimated to have weighed 70 kilograms, the size of ...

Low oxygen triggers moth molt

Aug 22, 2011

A new explanation for one of nature's most mysterious processes, the transformation of caterpillars into moths or butterflies, might best be described as breathless.

Cells die so defensive organs can live

Aug 04, 2011

Researchers demonstrate for the first time that programmed cell death - a process by which cells deliberately destroy themselves - is involved in mandibular regression in termites. And it appears this regression may be the ...

Some birds may use their feathers to touch

Feb 15, 2010

(PhysOrg.com) -- A new study of auklets suggests the birds use their ornamental feathers in much the same way as cats use their whiskers: to feel their surroundings.

Macaws face possible extinction

Oct 24, 2006

A U.S. bird expert says one of the world's most colorful birds -- the macaw, the largest member of the parrot family -- is in danger of becoming extinct.

Recommended for you

Fish found in suspected tsunami debris boat quarantined

8 hours ago

The wreckage of a fishing boat that appears to be debris from the 2011 Japanese tsunami was carrying some unexpected passengers—fish from Japanese waters—when it was spotted off the Oregon coast.

Roadkill hot spots identified in California

15 hours ago

An interactive map shows how California's state highway system is strewn with roadkill "hot spots," which are identified in a newly released report by the Road Ecology Center at the University of California, Da ...

Tagging and scanning for feral pigs

16 hours ago

Innovative research using GPS tracking and thermal imagery is being used in an attempt to manage the destructive behaviour of feral pigs in the south-west.

Mexico boosts protection of near-extinct porpoise

23 hours ago

Mexico is greatly expanding a protected area of the Gulf of California and boosting navy patrols in an effort to save the vaquita marina, a small porpoise facing imminent extinction.

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.