1. Nest Remains Show Birds Were the Kites' Most Common Prey
According to the Yamashina Institute for Ornithology, kites are often viewed as scavengers that eat fish or animal carcasses. Yet, during the breeding season, they actively catch birds, small mammals like mice, and snakes [1]. The clues to this behavior are found in the food remains left in their nests. In the Tokachi region of Hokkaido, analysis showed that 44% of the animals eaten were birds. Next, 32% were domestic animals such as cows, pigs, and sheep, while Yezo voles and red-backed voles were also found [1]. There are even cases where kites carry away baby birds along with their nests.
How should we interpret these numbers? The 32% figure for domestic animals does not necessarily mean the kites attacked living animals; they may have scavenged dead ones. Adding 44% and 32% gives 76%, leaving 24% for other animals like voles, though the exact breakdown is not detailed in the data. It is important to note that these figures come from nests in Tokachi and do not represent the ratio for the entire country. The institute suggests that kites likely use whatever food is most easily available in their specific region [1].
2. Do Kites Mainly Eat Dead Animals, or Is That Idea Wrong?
Do the two explanations contradict each other? The Abiko City Bird Museum states that a kite’s main food is dead animals, and they rarely attack large living animals [3]. A notice from Tottori Prefecture also says they mainly eat animal and fish carcasses, but also eat small living animals like frogs and mice, and even household waste in urban areas [2]. This differs in emphasis from the Tokachi nest study, which focused on the breeding season. Rather than one being wrong, it is natural to read these as different stories depending on the region, time of year, and size of prey. "Not attacking large living animals" and "catching small birds and mice" can both be true at the same time.
Similar explanations appear in New Zealand. The New Zealand Birds Online site describes the Black Kite (the English name for the kite’s relative) as an opportunistic raptor. Its core diet is carrion, but it also eats human garbage, shellfish, fish, small mammals, reptiles, insects, and birds, and sometimes steals food from other birds [6]. "Opportunistic" means taking whatever is available in the moment.
3. How Kites and Ospreys Hunt Fish Differently
Even among fish-hunting raptors, kites and ospreys have different methods. The osprey feeds mainly on fish, diving into the water from the air to catch them with its feet [3]. Kites, on the other hand, search for prey while flying, then dive steeply to scoop up their catch with their feet [4]. According to Canon’s bird guide, the osprey can dive into water and rise back up thanks to its thin, long wings. Other hawks and eagles often fail to take off after diving because their wings spread out on the water surface [5]. Since this is a corporate website explanation, it does not definitively state that kites cannot dive, but diving fishing does not seem to be the kite’s specialty.
To tell them apart, look at the tail. The kite’s tail has a slight notch in the center, distinguishing it from other hawks [3]. The Niigata Prefecture bird encyclopedia states that among Japanese raptors, the kite is the only one with a forked tail (where the tip is indented) [4].
4. Why Kite Chicks Near Food Sources Weighed More When Leaving the Nest
In the Tokachi survey, nests located in dense areas and closer to food sources, such as garbage dumps, had chicks that were heavier at fledging [1]. The average time chicks spent growing in the nest was 52 days. However, this varied greatly depending on food conditions, with some cases taking up to 78 days [1]. It appears that the availability of food gathering spots is linked to how long chicks take to leave the nest.
5. Why Kites Take Food From People
A researcher who observed kites in Kamakura reported that kites search for food from above, approach people holding food from behind, grab only the food, and fly away. The report suggests they are not attacking people but are obsessed with the food itself [1]. It is estimated that kites that were once fed by humans have developed the habit of taking food from people. This is an observation and estimation by the researcher.
Tottori Prefecture notes that kites that have tasted human food become obsessed with it. They recommend not feeding them, avoiding eating in open spaces with overhead clearance, eating under roofs, putting food in opaque bags, and using umbrellas to hide food [2]. Researchers also recommend hiding food with umbrellas or parasols [1]. Kites that have tasted human food may simply be applying their nature of choosing easily available items to human food as well.
This is an estimation based on the author’s observation, and it is not confirmed that feeding them is the sole cause.
6. How to Identify a Kite by Its Tail and Call in the Sky
In Japan, kites are distributed nationwide except for areas south of Amami and some islands, mainly inhabiting fishing ports, wide rivers, and farmland like rice paddies [1]. Try looking up at the sky above your local river or rice fields. There are two clues to look for. First, if the center of the tail is slightly indented, it is a kite [3]. Second, listen for the call. They make a clear, high-pitched call described as "pi-hyoro-ro-ro." During the breeding season, they often call while soaring with their wings spread like sails [1].
If you want to know more about their diet, the Yamashina Institute’s explanation notes that kites often use gloves and socks as nest materials, and they also eat insects near airports in winter. What kites eat reveals new faces when you observe them across different seasons and locations.