1. The Japanese white-eye, a 12 cm bird, eats nectar, insects, and fruits
In gardens, small birds can often be seen moving busily along the tips of tree branches. If a bird puts its face into a flower, one might assume it is sipping nectar. This bird is the Japanese white-eye, which has a total length of about 12 cm (about 4.7 inches) [1]. This size is slightly shorter than half of a standard 30 cm (about 12 inches) ruler.
Regarding its diet, an explanation of birds from Niigata Prefecture states that the Japanese white-eye feeds on insects, spiders, fruits, and flower nectar in trees [2]. Dictionaries and field guides also list insects, spiders, fruits, and flower nectar as part of its diet [1]. It is not a bird that eats only nectar.
These birds are often described as living in pairs or small groups [2]. If a bird that eats insects and fruits also sips flower nectar, how does it do so? The clue lies in its tongue.
2. The Japanese white-eye's brush-shaped tongue is used to take nectar
The tip of the Japanese white-eye's tongue is shaped like a brush. This tongue is explained as being suitable for taking fruit juice and flower nectar [1].
The bird's slender beak also helps in taking nectar. An explanation from the Honda Foundation's forest library notes that the Japanese white-eye inserts its slender beak deep into flowers and sips nectar intently [5].
Is this brush-shaped tongue common among relatives of the Japanese white-eye? In 1974, a researcher named Cooper in Australia reported with photographs that birds in the Zosterops genus (relatives of the Japanese white-eye) have a brush-shaped tongue with a forked tip [6].
However, the subject of that study was the silvereye relatives in Australia, not the Japanese white-eye itself. Furthermore, how the brush takes nectar (for example, by liquid creeping through tiny spaces, by surface tension, or by suction) is not explained for the Japanese white-eye in the materials used here.
3. What the Japanese white-eye eats in winter gardens and in spring
In winter, they come to eat tree fruits. According to the Honda Foundation, Japanese white-eyes eat tree fruits, tree buds, and insects in winter [5]. They are said to love sweet things, and when flowers bloom in spring, they happily come to sip nectar [5].
The Yamakuni River Office of the Ministry of Land, Infrastructure, Transport and Tourism also introduces that in winter, these birds come to garden trees in residential areas to eat tree fruits and sip flower nectar [3]. Canon's Bird Branch writes that in autumn and winter, they are easy to see because they come to gardens to eat tree fruits and enjoy nectar from flowers like the kantsubaki (winter camellia) [4]. Nectar from flowers that bloom in winter is also one of their foods.
The World Encyclopedia states that they sip nectar from camellia flowers and love ripe persimmons and akebi fruits [1]. Tree fruits and flowers in gardens seem to work as a winter feeding place for the Japanese white-eye.
However, they are not seen in winter everywhere. The materials introduce the Japanese white-eye as a resident bird or a wandering bird [1]. A wandering bird is one that moves locations within the country depending on the season. "They come to gardens in winter" is better read as a story about places where they are frequently seen.
4. Reference materials differ on what the Japanese white-eye's main food is
Even for the same Japanese white-eye, reference materials emphasize slightly different foods. Mypedia writes that insects and spiders are the main food, and they also eat flower nectar and ripe fruits [1]. Britannica writes that they also eat insects, but prefer flower nectar and fruit juice [1].
The Illustrated Encyclopedia NEO lists insects, spiders, fruits, and flower nectar side by side, without mentioning which is the main one [1].
The proportion of foods cannot be stated with numbers. Which food is "main" may change depending on the season, location, and time of observation. Since none of the materials used here show the proportion with numbers, this article does not state "what percentage." It is certain only that they are not birds that eat only nectar, nor birds that eat only insects, but that they use several types of food.
5. How to observe a Japanese white-eye's meals at the tips of branches in gardens and parks
If you see a Japanese white-eye, observe it quietly from a distance. Watch what its beak is pointing toward. Is it putting its face into a flower, pecking at branches or leaves, or feeding on a fruit?
Record what you see and what kind of tree it was. You might see whether the Japanese white-eye spends time on flowers or fruits. However, try not to decide the whole picture based on just a few accidental sightings.
Do not get too close; keep a distance where the bird does not flee. Do not pick flowers or fruits, or break branches.
Comparing dictionary entries (compiled on Kotobank) with bird explanations from Niigata Prefecture and the Ministry of Land, Infrastructure, Transport and Tourism [2][3] helps you understand how the description of food differs across materials.