Rain, Territory, and Misidentification: A Field Observation of Urban Spot-billed Duck Families on June 25, 2025

 

On June 25, 2025, I recorded a rainy-day field observation of multiple Eastern Spot-billed Duck families in an urban river environment. This footage is part of my continuous daily archive of wild duck family behavior, recorded mainly with Nikon P1100 and P950 super-telephoto cameras.

This is not a formal scientific study. I am not a professional ornithologist. However, by filming almost every day and preserving the original recording dates, family identification codes, and time-stamped behavioral notes, I try to leave a long-term observational record that can be reviewed later as evidence across dates.

This day was especially valuable because rain, changing water levels, and repeated encounters between duck families revealed several rare and difficult-to-interpret behaviors.

Featured organisms

- カルガモ / Eastern Spot-billed Duck / Anas zonorhyncha  

  The main species observed in this record. This urban wild duck raises ducklings in rivers, ponds, rice fields, and concrete waterways.

- ツバメ / Barn Swallow / Hirundo rustica  

  Several swallows were seen during the rain, possibly involving fledged juveniles. Their presence adds seasonal context to the river environment.

Observation setting

The date code for this record is 0625F, meaning June 25, 2025. The weather was unstable, with rain starting and stopping throughout the observation period. The river appeared to change gradually, and the water color seemed more reddish than usual, probably due to rainwater runoff and increased flow.

The main focus was the breeding area of several duck families. Some ducklings were independent or abandoned individuals, while others were still being guarded by their mothers. Because many families were active at the same time, identification was difficult, especially in the rain when feather patterns looked different.

Main observation 1: Af13 and repeated maternal absence

The Af family had 13 ducklings, now 47 days old. The family had moved downstream the previous day, but on this day they had returned upstream again. The mother was repeatedly absent, leaving the ducklings resting without her.

At 10:46, the Af mother returned. The family prepared to rest, but at 15:38 she flew away again. Later, at 27:27, she left the ducklings once more. This repeated absence may suggest a change in the mother’s behavior as the ducklings grow older.

One possible interpretation is that the mother was checking feeding sites, territory conditions, or nearby rival ducks. This is only my personal hypothesis, but the repeated flights and returns seemed more purposeful than random movement.

Main observation 2: A confusing attack on abandoned Df ducklings

One of the most unusual events occurred around 21:03–24:33.

The Af mother returned by flight but appeared to land near the abandoned Df ducklings instead of her own resting ducklings. The Df ducklings tried to avoid her. At 22:10, one duckling escaped by diving underwater, moving a surprisingly long distance.

At 22:41, one abandoned Df duckling was violently attacked by the Af mother. This scene is difficult to watch.

What made the behavior especially puzzling was the posture of the attacking bird. During the attack, the Af mother climbed on top of the duckling in a way that resembled mating behavior. The movement of the tail feathers just before separation also looked somewhat similar to mating behavior. While filming, I briefly wondered whether the bird might actually be a male, but based on later behavior and identification, it appeared to be the Af mother.

This may have been a case where territorial aggression, confusion, and physical dominance behavior overlapped. I cannot explain it with certainty. The important point is that the footage preserves the sequence: the mother returned, seemed to notice the wrong ducklings, chased them, attacked one, and then finally moved toward her own ducklings.

Fortunately, the attacked Df duckling later rejoined the others safely.

Main observation 3: Af13 descending the weir in the rain

At 36:07, Af13 began moving. The 13 ducklings followed the mother in a loose line. At 40:32, the family descended the weir.

Even though the ducklings had grown, the descent still looked somewhat difficult. I have observed this family descending the weir on rainy days several times, so this may be part of a recurring movement pattern. The mother may have been leading them toward a reliable feeding area downstream.

At 45:41, the family was feeding at a favored location. This strengthened my impression that large duck families may use specific feeding areas repeatedly, especially in wet weather.

Main observation 4: New family イf4

At 58:53, I found a family with four ducklings descending the weir. At first I thought it might be Lf4, but the mother’s appearance did not match. Because no other known four-duckling family clearly fit, I recorded this as a new family: イf4.

This identification is tentative. Rain changes the impression of feathers, and some mothers resemble one another strongly. Still, based on the available evidence, I treated this as a separate family.

Main observation 5: New family アf3 and conflict with Uf1

At 1:05:56, I found another new family with three very small ducklings. I recorded them as アf3-7, estimating the ducklings to be about seven days old.

This family later became involved in a long territorial conflict with Uf1, a mother with one duckling aged 15 days.

At first, the Uf mother seemed relatively tolerant. The アf mother repeatedly tried to move upstream but appeared afraid of the Uf family. She clearly noticed Uf several times and retreated. This showed how carefully mother ducks watch nearby families and how useful grass cover can be as a hiding place.

At 1:21:12, the Uf mother suddenly attacked. She appeared to attack both the アf mother and ducklings. One duckling seemed to be bitten briefly. After this, the conflict continued, and the アf family struggled to pass through the area.

At 1:33:40, after many attempts, the アf family finally found a route through the vegetation and escaped past the conflict zone.

This sequence suggests that tolerance between neighboring duck families may have limits. A mother may ignore another family at first, but repeated intrusion into a sensitive space can trigger strong aggression.

Other notable observations

Df捨4-39 was safe and resting calmly early in the recording.

Mf1-27 was seen resting without the mother, but the mother later returned. At another point, the duckling drifted downstream while the mother did not immediately notice.

Lf4-26 was safe and made a cute jump while landing for a rest.

Bf捨1-44 was seen near the previous location and avoided another duck.

Hf2-35 was found again in dense vegetation. The mother seemed to consider moving over the wall, and a relocation-like call was heard, but the ducklings ignored it.

Zf1-11 was safely observed again.

Yf3-22 approached the water gate area but turned back. One duckling appeared very wet and low in the water, and the mother allowed the family to rest on grass.

Cf3-44 and Uf1-15 were also confirmed safe.

Behavioral interpretation

The most important themes of this day were territory, misidentification, and pressure caused by rain.

Rain changed the river environment. Water flow became stronger, resting places were reduced, and some familiar sleeping spots were submerged. These changes may have forced families into closer contact than usual.

The Af mother’s attack on the abandoned Df duckling remains especially mysterious. It may have involved territorial aggression, mistaken recognition, or a dominance display that resembled mating behavior. I cannot determine the exact cause, but the behavior was rare and worth preserving as a dated observation.

The conflict between Uf1 and アf3 was easier to understand. It looked like a territorial boundary problem between two mothers with young ducklings. The younger アf family repeatedly tried to pass, and the Uf mother eventually became aggressive.

Conclusion

This June 25, 2025 record shows how complex urban duck family life can be during rainy weather. The river was not simply a peaceful habitat. It was a changing space filled with feeding routes, resting places, territorial boundaries, family recognition, and danger.

Because I record these observations daily and preserve the original date-based evidence, scenes like this can later be compared with earlier and later days. A single moment may look strange on its own, but when placed within a continuous archive, it may reveal patterns in movement, feeding behavior, maternal absence, territorial aggression, and duckling survival.

This footage contains painful scenes, especially attacks on ducklings, but it also documents an important part of wild behavior that is often hidden from casual observation.