Remarkable Teamwork in Spot-billed Ducks: A Mother Duck and Her Ducklings Drive Away an Intruding Duck

 Among the many behaviors observed in wild ducks, cooperative defensive behavior between a mother and her ducklings is one of the most fascinating. During this observation, I recorded a remarkable moment in which a female Eastern Spot-billed Duck confronted an unfamiliar duck approaching her family, only to be immediately followed by one of her ducklings in what appeared to be a coordinated second charge.

While this single event cannot establish scientific conclusions, it became one of many pieces of observational evidence collected through continuous day-by-day documentation of urban wild duck families. The same day's fieldwork also recorded developing independence in older ducklings, changing family distributions along the river, interactions with Little Egrets, Common Kingfishers, Azure-winged Magpies, and the ongoing movements of multiple duck families that have been monitored over several weeks.

This article is based on field observations made by an amateur wildlife observer rather than a professional ornithologist. Any interpretations presented here are personal hypotheses based on repeated observation and should not be considered definitive scientific conclusions.

Because nearly all of my daily recordings are published on the day they are filmed with minimal editing, they also serve as chronological evidence that cannot easily be altered afterward. Looking across many consecutive days often reveals behavioral patterns that would be difficult to recognize from a single observation alone.

The identification codes for duck families and filming date codes referenced throughout this project are explained here:

https://okasinaikimono.blogspot.com/p/welcome-to-wild-duck-diaries.html

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## A River Filled with Duck Families

By mid-July, numerous Spot-billed Duck families occupied different sections of the river simultaneously. Some families remained in the downstream pools below the weir, while others had already moved upstream or settled around quieter resting sites.

One challenge during this season is simply identifying each family correctly. As ducklings grow older, their appearance becomes increasingly similar, and several families with nearly identical brood sizes may rest only a few meters apart. Careful observation of the mother's wing pattern, behavior, and preferred resting locations becomes increasingly important for reliable identification.

Several families that had not been seen recently were successfully relocated during this survey, while a few others remained missing despite repeated searches.

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## Growth Visible in Everyday Movements

Several duckling groups demonstrated noticeably improved confidence when moving around the weir.

Only days or weeks earlier, some of these same ducklings hesitated before descending the concrete slope. During this observation, one family began sliding down voluntarily without waiting for the mother to lead.

Small behavioral changes like these are difficult to appreciate without continuous observation over many days. Watching the same families repeatedly makes gradual development much easier to recognize than dramatic single events.

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## A Rare Moment of Cooperative Defense

The most memorable observation occurred when an unfamiliar duck slowly approached one family.

The mother immediately reacted by charging toward the approaching bird. What caught my attention, however, was what happened next.

One duckling quickly followed behind its mother, seemingly joining the confrontation rather than retreating.

It would be inappropriate to conclude that the duckling intentionally assisted its mother, as many explanations remain possible. Nevertheless, the sequence produced the appearance of coordinated defensive behavior that was striking enough to document carefully.

Whether this represented learned behavior, simple imitation, or an instinctive response remains uncertain. Continued observation of similar situations may eventually reveal whether such "two-stage charges" occur regularly in older ducklings approaching independence.

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## Responses to Other Birds

The day's observations also highlighted how differently duck families respond to various bird species.

A Little Egret startled one duckling enough to produce a surprisingly loud alarm call despite its relatively small body size.

Later, an Azure-winged Magpie approached nearby vegetation, prompting visible vigilance from one mother duck. From repeated observations over multiple breeding seasons, I have noticed that mothers sometimes react strongly to Azure-winged Magpies, occasionally even more noticeably than to crows.

I have never personally witnessed an Azure-winged Magpie attacking ducklings, so I cannot conclude that such reactions indicate actual predation risk. However, experienced local observers have suggested that magpies may occasionally threaten small ducklings, particularly when moving in groups. This remains an interesting topic worthy of continued observation.

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## Returning Families and Missing Individuals

One particularly encouraging discovery was the reappearance of several families that had not been located recently.

Finding these families again provides valuable continuity within long-term observation records and helps confirm that they remain active within the river system.

Unfortunately, another family appeared to have one fewer duckling than during previous observations. Although the missing duckling could simply have become separated or dispersed naturally, it could no longer be located despite extended searching.

Because survival outcomes cannot be determined from a single day, I intentionally avoid drawing conclusions. Continued daily observation remains the most reliable approach for documenting what eventually happens.

Similarly, another family that had failed to climb the weir on the previous day could not be relocated despite searches of both tributaries and downstream sections. Based on previous years' observations, families occasionally relocate surprisingly long distances within a short period, so I remain optimistic that they may reappear in future surveys.

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## Other Wildlife Observed

Beyond the duck families, several other interesting species contributed to the richness of the day's observations.

A female Common Kingfisher rested quietly before later regurgitating a pellet, offering a brief glimpse into its feeding ecology. Looking into the shallow water from the kingfisher's perspective also revealed unexpectedly large numbers of small freshwater shrimp mixed among juvenile fish.

Moments like these remind me that even familiar urban rivers contain far more biological activity than is immediately visible from above.

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## Continuing a Long-Term Daily Record

This observation is only one entry within a much larger chronological record built through filming nearly every day.

Individual events may appear ordinary when viewed alone, but together they gradually reveal family movements, habitat use, developmental changes, seasonal dispersal, and countless small behaviors that would otherwise go unnoticed.

Although these observations are made by an amateur naturalist rather than a researcher, I hope that preserving complete daily records may become useful for future comparisons and perhaps even contribute, in a small way, to our understanding of urban wildlife.

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## Species Recorded

• カルガモ

  English: Eastern Spot-billed Duck

  Scientific name: Anas zonorhyncha

  A non-migratory East Asian dabbling duck well adapted to urban rivers, where prolonged parental care allows many aspects of family behavior to be observed.

• コサギ

  English: Little Egret

  Scientific name: Egretta garzetta

  A small white heron that feeds primarily on fish and aquatic animals in shallow water.

• カワセミ

  English: Common Kingfisher

  Scientific name: Alcedo atthis

  A highly specialized fish-eating bird known for its rapid diving and brilliant plumage.

• オナガ

  English: Azure-winged Magpie

  Scientific name: Cyanopica cyanus

  A social corvid often travelling in groups and frequently observed around urban green spaces.

• 淡水性エビ類

  English: Freshwater Shrimp

  Scientific name: Various species

  Important prey for many fish and waterbirds, often overlooked beneath the water's surface.