{"id":12591,"date":"2020-05-29T23:42:02","date_gmt":"2020-05-29T23:42:02","guid":{"rendered":"https:\/\/www.environment-hawaii.org\/?p=12591"},"modified":"2020-05-30T18:20:23","modified_gmt":"2020-05-30T18:20:23","slug":"as-habitat-is-lost-so-too-are-the-songs-of-kauai-forest-birds","status":"publish","type":"post","link":"https:\/\/environment-hawaii.org\/?p=12591","title":{"rendered":"As Habitat Is Lost, So, Too, Are The Songs of Kaua\u2018i Forest Birds"},"content":{"rendered":"\n
\"\"
An endangered \u2018akeke\u2018e.<\/figcaption><\/figure>\n\n\n\n

The distinctive vocalizations of three Kaua\u2018i honeycreepers are disappearing.<\/p>\n\n\n\n

Once, and not that long ago, an \u2018akeke\u2018e, or a Kaua\u2018i \u2018amakihi, or an \u2018anianiau could be identified by its song without setting eyes on the bird. Today, the calls of the three are so similar, you need visual confirmation to know which species you are hearing.<\/p>\n\n\n\n

And the birds\u2019 calls are not only growing increasingly similar. They\u2019re becoming simpler.<\/p>\n\n\n\n

The trends were reported in a paper published last year in the journal Royal Society Open Science<\/em>. The lead author is Kristina Paxton, a post-doc in the Listening Observatory for Hawaiian Ecosystems lab at the University of Hawai\u2018i-Hilo, under the direction of Patrick J. Hart, who is also a co-author of the paper, \u201cLoss of cultural song diversity and the convergence of songs in a declining Hawaiian forest bird community.\u201d<\/p>\n\n\n\n

As the authors note, \u201cthe reduction in song complexity and diversity and the convergence of songs not only signals a loss of culturally transmitted behaviors in these endemic Hawaiian honeycreepers, but also potential challenges to the recovery of these rapidly declining species.\u201d In addition, they write, their study of bird songs \u201chighlights the hidden cost to declining populations beyond just the loss of individuals that is not often considered, the loss of culturally transmitted social behaviors.\u201d<\/p>\n\n\n\n

Lost Cultural Diversity<\/strong><\/p>\n\n\n\n

In the late 1970s, Douglas H. Pratt, widely respected for his knowledge of Hawaiian birds, recorded the songs of Kaua\u2018i honeycreepers. The recordings were deposited with the Macaulay Library at Cornell University\u2019s Ornithology Lab, which provided the tapes of the Kaua\u2018i \u2018amakihi, the \u2018anianiau, and \u2018akeke\u2018e to Paxton and her colleagues to compare with recordings of the same species made in the early 2000s and in more recent years.<\/p>\n\n\n\n

When the frequencies and syllables of songs were plotted, the results were clear: For all three species, songs recorded in the 1970s were more intricate and distinct for each species than songs recorded in the present day. The songs recorded in the early 2000s were intermediate between the earlier and later periods.<\/p>\n\n\n\n

The authors describe how these trends are tied to the rapid decline in the birds\u2019 populations in their core ranges.<\/p>\n\n\n\n

At present, their range is limited to between roughly 5,000 and 10,000 hectares on Kaua\u2018i\u2019s Alaka\u2018i Plateau, less than a quarter of their maximum range in 1968. Their populations have fallen dramatically as well, due in large part to avian malaria. Between 1981 and 2012, the authors write, within the species\u2019 core ranges, the \u2018amakihi population fell 16 percent, that of the \u2018anianiau fell 17 percent, while that for the \u2018akeke\u2018e dropped by nearly half \u2013 48 percent. Fewer than 1,000 \u2018akeke\u2018e individuals are now thought to exist.<\/p>\n\n\n\n

\u201cSong diversity and complexity arises through the creation of new song elements during song learning via cultural mutations … and the cultural transmission of new songs among dispersing individuals,\u201d they write. \u201cHowever, based on changes in honeycreeper densities and range contractions during the course of this study, there was a two- to sevenfold decrease in the density of available tutors for Kaua\u2018i honeycreepers to learn from, along with a 60-77 percent reduction in the area from which young birds could sample songs.\u201d<\/p>\n\n\n\n

With regard to the birds\u2019 songs losing their complexity, one reason for it may be \u201crandom drift,\u201d with the songs of all three species \u201cconsisting of one to four unique syllables repeated on average over nine times … The loss of song complexity has led to present-day honeycreeper songs containing fewer unique syllables and fewer frequency changes within and among syllables,\u201d the authors say.<\/p>\n\n\n\n

Another reason could be that the birds of one species incorporate elements from the songs of the other honeycreepers as the young birds have fewer and fewer older birds of their own species to learn from. This could help explain why, even though densities of all three species have declined, density estimates for the \u2018akeke\u2018e and Kaua\u2018i \u2018amakihi are the lowest \u2013 and their songs were also the most similar, the authors write.<\/p>\n\n\n\n

Impacts on Reproduction<\/strong><\/p>\n\n\n\n

The cultural losses could well impact the survival of all three species. \u201cWhile the consequences of population declines are typically thought of in terms of the loss of genetic diversity,\u201d the authors note, \u201cthe disruption or loss of learned traditions can also affect species persistence, particularly when social learning is an important driver of behaviors that influence survival and reproduction.\u201d<\/p>\n\n\n\n

\u201cThe complexity of vocal signals such as song can serve as an honest signal of an individual\u2019s quality as well as the viability of a population,\u201d the authors write.<\/p>\n\n\n\n

Hart elaborated on that point. In the field of behavioral ecology, he said, \u201can honest signal is one that takes energy to perform. The ability to sing well may be an honest signal of a bird\u2019s fitness \u2013 it\u2019s doing well, eating well, had a good upbringing, grew up in a large population. It\u2019s a signal that they can\u2019t fake and can be used by other individuals to judge their fitness.<\/p>\n\n\n\n

\u201cUp to 30 percent of a bird\u2019s brain capacity has been shown to be related to song production and interpretation. It\u2019s reflective of their early years; if they grew up in a good environment and are fit, they\u2019ll have a more complex, desirable song.\u201d<\/p>\n\n\n\n

But why should the diminished richness of songs possibly lead to lower population growth?<\/p>\n\n\n\n

\u201cIt\u2019s hard to say for sure,\u201d Hart said. \u201cIt just may be that it doesn\u2019t entice mating as much. Just like with humans, the song is supposed to entice the female to want to come and mate.\u201d<\/p>\n\n\n\n

What\u2019s more, Hart and his co-authors suggest the impoverishment of the honeycreepers\u2019 songs and their convergence \u201ccould lead to a breakdown in species barriers.\u201d<\/p>\n\n\n\n

Does that mean that hybridization is possible among these species?<\/p>\n\n\n\n

\u201cWell, yes, I think it is definitely a possibility,\u201d he said. \u201cWe know that \u2018i\u2018iwi and \u2018apapane can hybridize. Kaua\u2018i birds are closely related. If a young \u2018akeke\u2018e mostly learns songs of \u2018amakihis, then it might be attracted to an \u2018amakihi song when it\u2019s an adult, since that\u2019s what it knows more.<\/p>\n\n\n\n

\u201cThey\u2019re learning each other\u2019s songs, which leads to a higher potential for hybridization,\u201d he said. Or, he said, alternatively, a male and female from different species could pair up but fail to have any offspring at all.<\/p>\n\n\n\n

\u201cNeither possibility is good.\u201d<\/p>\n\n\n\n

Songs of the \u2018Alala<\/strong><\/p>\n\n\n\n

The loss of song complexity has been observed in other species, including the \u2018alala, the Hawaiian crow. Ann Tanimoto, a graduate student working closely with Hart, examined differences in the vocal repertoire of \u2018alala in the wild, recorded in the early 1990s, from those held in captive breeding aviaries.<\/p>\n\n\n\n

\u201cThey lost a lot of elements,\u201d Hart said. \u201cWhole things like territorial songs, things like that, had just disappeared in the aviaries. Now we\u2019re tracking the individuals released into the wild and how their songs are becoming much more rich and complex again.\u201d<\/p>\n\n\n\n

Hart said one of his grad students continues to go twice a week to the area where the \u2018alala were released, \u201cvideoing the \u2018alala, cataloguing all their vocalizations, looking at dominant and non-dominant birds, and comparing it to the aviary birds.\u201d<\/p>\n\n\n\n

In another study, students from Hart\u2019s lab compared the songs of \u2018amakihi in a low-elevation population on the Big Island with those of populations in mid- to high-elevation sites. \u201cThe reduced complexity of \u2018amakihi songs at low-elevation sites is most likely shaped by the effects of habitat fragmentation and a disease-driven population bottleneck associated with avian malaria and maintained through isolation, localized song learning and sharing, and cultural drift,\u201d wrote authors Joshua Pang-Ching, Kristina Paxton, Eben Paxton, Adam Pack, and Hart (\u201cThe effect of isolation, fragmentation, and population bottlenecks on song structure of a Hawaiian honeycreeper,\u201d Ecology and Evolution<\/em>, 2018). (The Hawai\u2018i \u2018amakihi is a different species from the Kaua\u2018i \u2018amakihi.)<\/p>\n\n\n\n

For more information on the work Hart and his colleagues are doing, visit the LOHE website: www.lohelab.org.<\/p>\n\n\n\n

\u2014Patricia Tummons<\/strong><\/p>\n","protected":false},"excerpt":{"rendered":"

The distinctive vocalizations of three Kaua‘i honeycreepers are disappearing. Once, and not that long ago, an ‘akeke‘e, or a Kaua‘i ‘amakihi, or an ‘anianiau could be identified by its song without setting eyes on the bird. Today, the calls of … Continued<\/a><\/p>\n","protected":false},"author":1,"featured_media":12614,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[26,470],"tags":[7],"class_list":["post-12591","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-endangered-species","category-june-2020","tag-patricia-tummons"],"_links":{"self":[{"href":"https:\/\/environment-hawaii.org\/index.php?rest_route=\/wp\/v2\/posts\/12591","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/environment-hawaii.org\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/environment-hawaii.org\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/environment-hawaii.org\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/environment-hawaii.org\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=12591"}],"version-history":[{"count":0,"href":"https:\/\/environment-hawaii.org\/index.php?rest_route=\/wp\/v2\/posts\/12591\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/environment-hawaii.org\/index.php?rest_route=\/wp\/v2\/media\/12614"}],"wp:attachment":[{"href":"https:\/\/environment-hawaii.org\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=12591"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/environment-hawaii.org\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=12591"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/environment-hawaii.org\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=12591"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}