Molt patterns, aging criteria, and molt-breeding seasonality of 8 native forest birds from the Island of Hawai‘i

ABSTRACT Much of our knowledge on the patterns and timing of breeding and molting come from studies of temperate region birds, yet tropical birds can have markedly different phenologies. The Hawaiian Islands support multiple endemic bird species that have evolved for millions of years in isolation to a tropical environment with minimal seasonality. We examined data from multiple studies (1994–2020) conducted across the avian annual cycle, from multiple locations, to evaluate molt patterns and establish criteria for assignment of age and sex based on the WRP, or molt-cycle age classification system designed specifically for tropical species. In addition, we describe the phenologies of molt and breeding and quantify the differences in males and females based on plumage coloration and morphometrics for 8 native species. We were able to validate the WRP tropical bird aging system as an appropriate method for aging forest birds from the Island of Hawai‘i and separate all 8 species examined into juvenile, formative, and definitive plumages based on feather patterns and molt limits. Additionally, 2 species had distinctive second basic plumages. All 8 species examined also had extended periods of breeding and molting unlike their familial temperate counterparts, but these high-energy activities are largely partitioned into separate time periods. Each species had some degree of overlap in breeding and molting, but the frequency of individuals that were simultaneously in breeding condition and molting was low with only 2 species displaying a proportion of overlap greater than 10% among all captures. Accurate aging and sexing techniques improve the quality of data from banding studies and provide important information on how species adapt to their environments. HŌ‘ULU‘ULU MANA‘O (Hawaiian) ‘O ka nui o ka ‘ikepili no ke ‘ano a me ka manawa o ka hānau keiki ‘ana a me ka māunu ‘ana o nā manu, ua loa‘a mai ke kālailai ‘ana i nā manu o nā ‘āina kemepale. ‘O nā manu kopikala, he ‘oko‘a loa ko lākou pō‘aiapuni ola. Ma ka hala ‘ana o nā makahiki he mau miliona, ua liliuewe mai he mau lāhulu manu ‘āpa‘akuma ma Hawai‘i pae ‘āina nei, he ‘āina kopikala i loa‘a ‘ole nā kau kemepale. Ua kālailai māua i ka ‘ikepili mai nā atikala he nui ma waena o ka makahiki 1994 a i ka makahiki 2020. He mau ‘atikala kālailai ia i nā pō‘aiapuni ola o nā manu o kekahi mau ‘āina ‘oko‘a i mea e kālai ai i ke ‘ano o ka māunu ‘ana o nā manu, a i mea ho‘i e ho‘okahua ai i nā kūlana pa‘a e maopopo i ke keka a me ka nui makahiki o nā manu ma ke ‘ano kūmau o ka ‘ōnaehana WRP. He ‘ōnaehana ka WRP e hō‘oia ai i ke ‘ano o ka wā māunu a me ke kūlana makahiki o nā manu kopikala. Eia ho‘i, ua wehewehe māua i ka pō‘aiapuni o ka wā māunu, a me ka pō‘aiapuni o ka hānau keiki ‘ana o nā manu i kālai ‘ia. Ua helu ho‘i māua i ka ‘oko‘a o nā manu kāne a me nā manu wahine o ‘ewalu mau lāhulu manu Hawai‘i ma ke ‘ano o ka waiho‘olu‘u o ka hulu a me nā ‘oko‘a ‘ē a‘e o ke kino. Ua hō‘oia māua i ke kūpono o ka WRP i ‘ōnaehana hō‘oia kūlana makahiki ma kona ‘ano he ki‘ina hana e hō‘oia ai i ke kūlana makahiki o nā manu nahele o ka mokupuni ‘o Hawai‘i. Ua wae‘ano nō māua i nā manu a pau o nā lāhulu ‘ewalu i kālai ‘ia ma ke ‘ano o ka hulu a me ke ‘ano o ka māunu ‘ana; ‘o ia mau ‘ano o ka hulu, he hulu kuapo‘i, hulu ‘ōpiopio, a he hulu makua. Eia ho‘i, he ‘elua mau ‘ano hulu makua ‘ana ko ‘elua o nā lāhulu manu. Ua ‘oko‘a nā lāhulu manu ‘ewalu a pau mai ke ‘ano o nā manu kemepale i ka ‘oi lō‘ihi o ko lākou mau wā hānau keiki a me ko lākou mau wā māunu. He ka‘awale na‘e ia mau wā kekahi mai kekahi, no ka ho‘oluhi nui paha i ke kino o ka manu. Kaulapa iki nā wā hānau keiki a me nā wā māunu o kekahi mau manu o ia mau lāhulu, ‘a‘ole na‘e i nui loa nā manu e hana pēlā. He ‘elua wale ho‘i mau lāhulu i ‘oi nui ia kaulapa ‘ana ma ‘umi pakeneka a ‘oi o nā manu i hopu ‘ia. He kōkua nui ka ‘oi maika‘i o nā ki‘ina hana hō‘oia keka a me nā ki‘ina hana hō‘oia kūlana makahiki i ka hō‘oia‘i‘o i ka ‘ikepili i ‘ohi‘ohi ‘ia ma nā kālailai ho‘okolo manu. He ko‘iko‘i ia ‘ikepili e maopopo ai kākou i ka liliuwelo o nā lāhulu manu i ko lākou mau wahi pono‘ī.