Palila inhabit dry subalpine forest, preferring areas with native ground cover. The favored understory typically includes endemic species such as pukiawe (Leptecophylla tameiameiae), a shrub usually around a meter tall, and a few native grasses and sedges. The birds exclusively live in mamane (Sophora chrysophylla) or mixed mamane-naio (Myoporum sandwicense) woodlands, preferably with mature trees and high canopy cover. The mamane and naio are shrub-like trees, usually reaching 15-20 meters in height. (Hess, et al., 2014; Johnson, et al., 2006; Reddy, et al., 2012; Scott, et al., 1984)
The palila are considered a large finch around 19 centimeters long and weighing 35 grams on average. They have gray backs, and a white ventral area, with a yellow head and breast. Gray flight and tail feathers are edged in green. Palila are considered sexually dichromatic, with males having an overall brighter colorization of their head and breast, and a distinct napeline between the yellow head and grey back. Females have a duller greenish yellow head and neck, with an indistinct napeline. The lores of females are dull grey while black in males. There are no seasonal variations and the birds molt once per year.
Male and female birds under a year both have a more dull yellow head and breast, and also have double barring on their secondary and primary coverts. Palila have a curved blunt bill, with the tip being yellow as a nestling, white as a juvenile, and black in adult birds. They have brown irises and black legs. (Jeffrey, et al., 1993; Pratt, et al., 2005)
Palila are monogamous breeders, and breeding pairs frequently stay together for consecutive seasons. The birds have high nesting site fidelity, and often return to nest in an area within a 1 kilometer range of their previous nesting site. First time breeders are also known to return within 1 kilometer of where they fledged, with females more likely than males to disperse further. Nesting sites are also chosen based on food availability, and breeding may be delayed during years of low production. Courtship of palila involves males advertising with low short glides and slow wing flutters, while females solicit feedings from males with wing quivering and vocalizations. Males will feed females during courtship and through incubation, and may chase females during the early breeding season. Nest territory is defended by males through chasing intruding males away from the nest and female, or by song. The range of the defended nesting territory has been recorded around 3900 square meters during breeding, but reduced to 600 square meters during incubation. After the young have fledged, all birds rejoin their feeding flocks. (Fancy, et al., 1997; Jeffrey, et al., 1993; Van Riper III, 1980)
The palila breeding season may last 6-8 months and begins in March or April. Peak nesting occurs in April – July, but is reliant on availability of food resources. Breeding will be delayed if food is limited. Nests are built in mamane trees, and males and females both assist in building cup nests. Nests consist primarily of sticks, grasses, and some lichens, and have been recorded taking anywhere from 7 to as long as 20 days to build. Females tend to lay during the early morning, and one egg is laid per day. Clutch size can be 1-4 eggs but 2 eggs are more common. Palila have been reported as determinate layers, and will not replace an egg that has been removed from the nest. Incubation lasts 16-17 days, with the average nestling period lasting 25 days. The growth of the palila is slower than most other passerines, but result in fledglings that are strong fliers. Young palila leave the nest for nearby branches, but returned each evening approximately one week before fledging. Parents continue to feed fledglings up to a week, but young birds often remain with parents up to thirty days after fledging. A second brood may be attempted by the same breeding pair, but is statistically less successful than the first, with earlier season broods having four times more success than late season. (Fancy, et al., 1997; Laut, et al., 2003; Pletschet and Kelly, 1990; Pratt, et al., 1998; Van Riper III, 1980)
Males and females both contribute in building the nest, but females exclusively incubate and brood the chicks. Males will assist in feeding the female during incubation, and some pairs are aided by a secondary male helper, which may provide food to the female and chicks during the incubation and nestling stages. This behavior may be a side effect of the skewed sex ratio of the palila. More attention in regards to time is given to the eggs than to the nestlings by the female. After hatching the female removes the egg shells. Fecal matter is removed from the nest for the first few days, and then mostly allowed to accumulate, removing it only from the bowl of the nest. Feedings appeared to decrease as nestlings grew, and females take longer recesses away from the nest in correlation to nestling age. Young chicks take on average 25 days to fledge, but may remain with parents in post-breeding flocks for upwards of 30 days. New fledglings remain relatively inactive for the first week, often staying on one tree, and parents will continue to feed their offspring during this time. Parents may attempt a second brood, even while feeding the first, however this can sometimes be met with complications. The first fledged offspring have been known to flush the adults off the nest, exposing the eggs to the environment, or disrupting the young nestling’s feedings. (Laut, et al., 2003; Pletschet and Kelly, 1990; Pratt, et al., 1998; Van Riper III, 1980)
No reports of lifespan was available from the literature, however some birds have been noted to live at least until 13 years of age. (Banko, et al., 2020)
Palila are non-migratory birds with limited movements in their small range, because of this they are slow to recolonize restored habitat. Flocks are denser before and after breeding season, but relatively small. They are generally seen in groups of around five birds, which are thought to be family units. Palila are generally non-territorial, but are not social with each other aside from the breeding season, during which males will feed females during courtship and incubation. Palila spend 40% of their daily activity foraging for food, with most of their foraging time spent in mamane trees. (Fancy, et al., 1997; Hess, et al., 2014; Johnson, et al., 2006; Pratt, et al., 2005; Van Riper III, 1980)
Palila have a total range estimated to be 30 square kilometers of the western slope of Mauna Kea on the island of Hawaii. Nesting territory is only defended during the breeding season and is approximately 3900 square meters, which reduces to 600 square meters during incubation. (Banko, et al., 2002b; Scott, et al., 1984; Van Riper III, 1980)
Palila have a variety of songs that include whistles, warbles, trills and chirps, and sometimes mimic the songs of other species in their range. Increased singing is noted during the breeding season performed by males, mostly to defend nest sites and females from other males, however palila are generally non-territorial. With an upward warble on the first two notes and a downward inflection on the third, the Palila’s common song mimics the phonetics of its name. Communication during courtship is also done with low flutter-and-glide flights from males, and with wing fluttering from interested females. (Johnson, et al., 2006; Pratt, et al., 2005; Van Riper III, 1980)
The palila diet primarily consists of mamane (Sophora chrysophyll) seed pods, but also the plant’s young leaves, and flowers. They are highly specialized eaters, and after securing a pod will return to a suitable perch, hold down the pod with one or both feet, and use their beaks to tear open the tough protective layer to eat the green cotyledons and germ of young seeds. 40% of their day is spent foraging, with 95% of their foraging time spent in mamane trees. Palila follow mamane pod production as it moves in elevation throughout the year. When mamane availability is low, they will eat the fruit of the naio (Myoporum sandwicense) and a small amount of other plant material. Lepidoptera larvae is also an important part of their diet. They have not been directly observed eating them, but Cydia spp. is often found in fecal analysis. (Banko, et al., 2002a; Hess, et al., 2014; Kildisheva, et al., 2013)
Non-native rats, mice, mongoose, and feral cats are all predators to palila, along with native short-eared owls, also known as pueo (Asio flammeus sandwichensis). Palila have no known defenses to predaceous mammals as the mammals are relatively new to the Hawaiian Islands, and therefore the birds have developed no evolutionary response to their presence. There is some debate on how much effect rats have on the native finches, as their population densities are greater in lower elevations, notably with microhabitats of grasses and naio that the palila are absent from, but some egg predation by rats has been recorded. Feral cats are noted to have the most predation events on palila, typically during the nestling period when both young birds and brooding females are relatively easy to catch. Invasive mosquitos are a known problem of many Hawaiian honeycreepers as they transmit avian pox and avian malaria while feeding on the birds, however the geographic range of palila is usually at a higher elevation than mosquito populations. Mosquitoes that transmit the virus typically remain below 1500 meters in elevation, while the palila live above 2000 meters. (Amarasekare, 1994; Banko, et al., 2002a; Banko, et al., 2013; Lindsey, et al., 1995; Pratt, et al., 1998)
Hawaiian honeycreepers are pollinators, and the Palila is no different. While not nectivorous, they feed almost exclusively on the mamane tree, particularly its seed pods and flower parts. In addition to pollinating they likely aid in seed dispersal. Palila have likely evolved to eat the pods of the mamane tree, as they have high levels of toxic alkaloids, which are noted to interfere with the central nervous system channels in most other animals. Plants produce these as a defense mechanism against herbivores. They are in competition with the moth larvae from the Cydia genus which also feeds on the mamane plant, however the larvae is also a prey item to the palila. Palila are preyed on by the Hawaiian short-eared owls and non-native mammals but are not the main food source for any one species. (Banko, et al., 2002b; Banko, et al., 2002a; Lindsey, et al., 1995)
There are no known economic benefits to humans, however palila may provide an ecotourism role as one of the remaining species of honeycreepers endemic to Hawaii. Birders are beginning to play an important part in tourism revenue in other areas of the world, particularly in regards to endangered species. This in turn helps boost the local economy, and potentially allocates funds back into conservation. (Steven, et al., 2013)
There are no known negative economic effects on humans, however the forest where the palila live is also inhabited by feral sheep, which graze and reduce the mamane habitat that the finches rely on. Attempts to eradicate the sheep in the past have been met with resistance, as they are a source of income from game hunting, which would be lost with their removal. (Banko, et al., 2001; Banko, et al., 2013; Banko, et al., 2014; Ikagawa, 2013)
Palila are currently listed as critically endangered by the IUCN Red List with a declining population. Yearly fluctuations of population size is dependent on weather conditions and food availability, however the population has continued to remain around 2000 individuals. Listed as critically endangered by the U.S. Fish and Wildlife Service in 1967, threats to the palila include loss of habitat from human activity, loss of habitat due to browsing by feral sheep and goats on the main Hawaiian island, and increasing years of drought due to climate change, which results in lower mamane seed production. Efforts to preserve the species have primarily included both public hunting, and aerial shooting to eradicate the feral ungulates, and funding provided by the USFWS to fence critical habitat to prevent the sheep and goats from further browsing. There has been positive recovery of ideal habitat, specifically the mamane trees that the palila rely on, following eradication of the browsers from their habitat. Re-introduction of palila to the eastern side of Mauna Kea has also been attempted, and did result in minimal nesting success, however due to the bird’s nesting site fidelity, many mating pairs returned to their original nesting areas on the western slope. Long term management will likely be required for the continued survival of the species, including continuation of population monitoring efforts. (Banko, et al., 2001; Banko, et al., 2013; Banko, et al., 2014; Fancy, et al., 1997; Hess, et al., 2014; Johnson, et al., 2006; Reed, et al., 2012)
Chandra Rasset (author), Northern Michigan University, Alec Lindsay (editor), Northern Michigan University, Tanya Dewey (editor), University of Michigan-Ann Arbor.
uses sound to communicate
young are born in a relatively underdeveloped state; they are unable to feed or care for themselves or locomote independently for a period of time after birth/hatching. In birds, naked and helpless after hatching.
Referring to an animal that lives in trees; tree-climbing.
having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.
uses smells or other chemicals to communicate
helpers provide assistance in raising young that are not their own
humans benefit economically by promoting tourism that focuses on the appreciation of natural areas or animals. Ecotourism implies that there are existing programs that profit from the appreciation of natural areas or animals.
animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.
parental care is carried out by females
an animal that mainly eats leaves.
forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.
an animal that mainly eats seeds
An animal that eats mainly plants or parts of plants.
animals that live only on an island or set of islands.
offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).
parental care is carried out by males
Having one mate at a time.
having the capacity to move from one place to another.
the area in which the animal is naturally found, the region in which it is endemic.
islands that are not part of continental shelf areas, they are not, and have never been, connected to a continental land mass, most typically these are volcanic islands.
reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.
breeding is confined to a particular season
remains in the same area
reproduction that includes combining the genetic contribution of two individuals, a male and a female
uses touch to communicate
Living on the ground.
the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.
uses sight to communicate
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