Duckling Rejoins Its Original Family After Brood Mixing: Eastern Spot-Billed Duck Reunion and Maternal Absence

 A young Eastern Spot-billed Duck that had become separated from its mother, joined another brood, and later disappeared from that foster family was observed alive with its probable original family two days later. The same field session also documented ducklings waiting quietly after their mother flew away, an unusually slow family movement through the river, and a young duck leading its mother over a small drop.

This account is based on continuous video documentation and comparisons with records from the preceding days. It is not a formal scientific study, but a field observation by a non-specialist who records local duck families almost every day. Individual identifications and behavioral interpretations are therefore presented cautiously, together with the evidence and uncertainties on which they are based.

## Field Observation Video




## Main Species Observed

- カルガモ — Eastern Spot-billed Duck — *Anas zonorhyncha*  
  A common East Asian duck whose females raise the young without assistance from the male. Similar-looking mothers and older ducklings can be difficult to distinguish, so repeated observation of plumage, family size, location, and behavior is important.

- ハシボソガラス — Carrion Crow — *Corvus corone*  
  A highly adaptable crow frequently seen in urban and riverside environments. Two individuals resting inside vegetation may have been a pair, although this could not be confirmed from the footage alone.

- アオサギ — Grey Heron — *Ardea cinerea*  
  A large wading bird that feeds on fish, amphibians, and other small animals. Its presence near resting ducks does not always cause an obvious alarm response, although reactions can differ greatly between duck families.

- コイ — Common Carp — *Cyprinus carpio*  
  A large freshwater fish widely established in urban rivers. Carp were visible close to resting ducklings during this observation, but no aggressive interaction was recorded.

- ウシガエル — American Bullfrog — *Lithobates catesbeianus*  
  A large introduced amphibian whose deep calls have become increasingly noticeable at this site in recent years. Its apparent local increase is based on my personal sound records rather than a formal population survey.

- カワセミ — Common Kingfisher — *Alcedo atthis*  
  A small fish-eating bird known to regurgitate pellets containing indigestible material. No kingfisher was central to this event, but its pellet-casting motion provided a useful comparison for an unusual movement made by one duckling.

## A Probable Reunion After Brood Mixing

The most significant observation of the day concerned the family recorded as キf4-7: mother キf with four ducklings at approximately seven days old.

Two days earlier, this family had become divided. The mother remained with three ducklings, while four separated young were observed away from her. During the subsequent events, two of the separated ducklings were taken by fish, another disappeared, and the final visible survivor approached the area where its mother was present but did not successfully reunite with her.

That last duckling later joined the family ケf2, an unusual example of temporary brood mixing involving a very young duckling. On the following day, however, ケf was once again accompanied by only two young. The fate of the additional duckling was therefore uncertain.

At 20:42 in the present record, mother キf was found with four ducklings.

This observation strongly suggests that the temporarily adopted duckling survived and returned to its original family. The conclusion cannot be treated as absolutely proven because the young were not individually marked. In theory, the fourth duckling could have been the individual that had disappeared earlier. However, mother キf had continued downstream with three young after the near encounter, making that alternative appear less likely.

The reconstruction is therefore based on several forms of circumstantial evidence:

- the previously confirmed separation of the brood;
- the temporary presence of an additional duckling with ケf;
- the return of ケf to its original brood size;
- the later appearance of four young with キf;
- the timing and movement of the families across consecutive observation days.

For an unmarked wild bird, this sequence provides unusually strong chronological evidence of survival and probable reunion.

## A Duckling Leads Its Mother Down the Drop

Earlier in the observation, ケf2-7 was found near a small floodgate where the family had also been seen the previous day. Duck families have occupied this location in earlier years, but no family had settled there during most of the current season.

One possibility is that this family had been carried downstream during increased river flow and was unable or unwilling to return to its earlier range. This remains speculation based on its location and recent river conditions.

At 09:41, one duckling appeared strongly motivated to descend a small step and moved ahead of its mother. The mother initially seemed more inclined to climb, and at 10:38 she led the young in the opposite direction.

The duckling persisted. At 11:19, it jumped down the step, after which the mother followed.

It would be easy to describe this as the duckling “winning” a disagreement, but such human language should not be taken literally. The observable facts are simpler: the young bird repeatedly approached the lower route, descended first, and was then followed by its mother.

After the descent, the family swam downstream exceptionally slowly. This relaxed pace was notable because families passing through narrow or exposed sections often move more quickly and remain tightly organized.

## Peaceful Mixing Within a Large Duck Gathering

At the beginning of the record, many ducks were resting and swimming together in shaded areas. Some may have belonged to the older Af brood at approximately 70 days old, but the individuals could not be identified confidently.

At 04:03, Lf4-50 entered the larger group without provoking an obvious conflict. The four young passed through the gathering normally, and the family later moved to a raised summer resting structure.

Broods of similar age can sometimes remain close to unrelated ducks without incident. This peaceful scene is easy to overlook, but it is useful behavioral evidence because encounters between mothers, juveniles, and unfamiliar broods can also lead to displacement or aggression.

## Four Ducklings Wait After Their Mother Flies Away

After the probable reunion was confirmed, キf4-7 rested on a small island. The ducklings preened, slept, and gathered close to their mother.

At 28:41, one duckling disappeared almost completely beneath the mother’s shadow and body. Moments like this can make exact brood counts difficult, particularly when vegetation, overlapping bodies, and strong sunlight obscure small young.

At 29:28, the mother suddenly flew away, leaving all four ducklings behind.

The young did not scatter or immediately attempt to follow. Instead, they remained together and waited quietly at the resting site. Their calm behavior suggests that temporary maternal departures may be familiar or that remaining motionless as a group is an effective response when the mother is absent.

At 43:35, the mother returned. The ducklings appeared to react before the audible sound of her landing was recorded clearly, possibly detecting her approach visually or through subtler sounds.

The family reunited and departed at 44:01.

The mother’s absence lasted approximately fourteen minutes in the recorded sequence. Because the camera remained focused on the waiting young, this provides a relatively complete record of their behavior during a temporary separation.

## An Unusual Gagging or Regurgitation-Like Movement

At 31:19, one duckling repeatedly made a movement resembling gagging or an attempt to bring material upward.

The action reminded me of the motion made by a Common Kingfisher when regurgitating a pellet. Ducks can expel indigestible or irritating material, but I did not see any object leave the duckling’s bill, and I have not documented a definite pellet being produced by a duck at this site.

For that reason, the footage should be described only as a regurgitation-like or gagging motion. Possible explanations include the adjustment of food in the throat, irritation, drinking-related movement, or an unsuccessful attempt to expel material.

The behavior deserves comparison with future records, but the present video alone is not sufficient to determine its cause.

## Ducklings Resting Beside Large Carp

At 40:22, large carp passed close to the resting ducklings without causing a visible alarm response. The young remained calm and continued resting.

This was particularly striking because one member of the brood had probably been present when ducklings from the separated group were taken by fish two days earlier. However, it is not possible to know whether the surviving duckling understood the earlier event as predation or recognized a general danger from large fish.

The family had also returned to the area associated with the previous attacks. This location is normally a favored resting place when the river level is lower. The attraction of a familiar, sheltered resting site may therefore have outweighed any avoidance response.

This should not be interpreted as evidence that the ducklings had “forgotten” the danger. It simply shows that no obvious fear response was visible during this encounter.

## Other Families Confirmed During the Survey

The purpose of the daily survey was not limited to a single family. I searched for as many known broods as possible in order to document survival, movement, changes in brood size, and shifts in territory.

Families confirmed during this recording included:

- Lf4-50, resting among other ducks and later sleeping in shade;
- ケf2-7, still using the small floodgate area;
- Of2-47, with the young continuing to develop normally;
- Mf1-50, whose nearly grown juvenile was becoming increasingly difficult to distinguish from unrelated ducks;
- キf4-7, providing the most important reunion evidence of the day;
- イf4-46, resting on the opposite bank;
- Uf1-38, located in a nursery area after being missed the previous day;
- Tf8, resting in two groups of four.

Several other known families could not be found, including クf5 and コf3. They may have moved downstream, but absence from a survey does not establish disappearance or mortality.

Hf2, Zf1, カf1, and ウf1 were also not confirmed. カf1 had been present the previous day, so a local movement caused by the arrival of another family is possible.

## Seasonal Changes in Family Distribution

The rapid appearance of new summer broods has increased the number of families using the river at the same time. Tf8, a relatively large family, has also expanded its activity range.

These changes appear to be affecting the distribution of families already present. Resting sites, shaded areas, narrow channels, and sheltered banks are limited resources. Even when direct fighting is not observed, the arrival of new broods may cause established families to shift their daily routes.

At 58:12, many ducks were gathered beneath a bridge. Cf mother was visible without her young and may already have become independent from them. Several females with distinctive plumage were also examined, but none could be matched confidently to the missing broods.

This gathering may be related to the approach of the major seasonal molt, when adult ducks become less mobile and often concentrate in safe resting areas. However, individual plumage changes during this period make identification increasingly difficult.

I have repeatedly noticed that some mothers appear to undergo a sudden change in the visible pattern of the tertial feathers near the end of brood care. My current assumption is that loosening, loss, or replacement of feathers before molt alters the pattern used for identification. This remains an amateur field hypothesis and requires more repeated photographic comparisons.

## Limits of Identification

None of the ducks in this project are captured, tagged, or physically marked. Identification is based on non-invasive visual evidence, including:

- patterns in the mother’s tertial and wing feathers;
- brood size;
- estimated age of the young;
- repeated routes and resting sites;
- behavior toward neighboring families;
- continuous comparison with footage from preceding and following days.

This method can produce strong evidence, but it cannot eliminate every possibility of mistaken identity. As ducklings grow and mothers begin to molt, confidence may decrease.

For this reason, uncertain identifications are stated as probable rather than definite. The probable reunion of the キf duckling is supported by a particularly informative sequence across several days, but it remains an inference from unmarked wild animals.

## Why Consecutive Daily Records Matter

A single video would show only a mother with four ducklings. It would not reveal why the fourth young was important.

The significance became visible only by comparing records across multiple dates:

1. the original family became divided;
2. several separated young disappeared or were preyed upon;
3. one survivor temporarily joined another brood;
4. that foster family later returned to its previous brood size;
5. the original mother was subsequently found with four young.

Daily recording turns separate encounters into chronological evidence. Upload dates, field notes, brood counts, and largely unedited footage together preserve the sequence in which events were observed.

This project is not conducted by a professional ornithologist, and the interpretations should not be treated as peer-reviewed conclusions. It is a long-term natural history record created by an independent observer who documents the same river system, individuals, and family groups as consistently as possible.

## Observation Code Information

The filming date code for this record is 0718F.

In this code system:

- 0718 represents July 18;
- F represents the year 2025.

Duck family codes combine the identity assigned to the mother, the observation year, the number of ducklings, and their estimated age.

For example:

- キf4-7 = mother キf, four ducklings, approximately seven days old;
- Lf4-50 = mother Lf, four young, approximately 50 days old;
- Uf1-38 = mother Uf, one young, approximately 38 days old.

The Katakana characters used in codes such as キf and ケf are independent mother-identification symbols. They must not be converted into Roman letters.

A full explanation of the date codes, duck family identification system, and the purpose of this long-term observation project is available here:

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

The mother-duck identification reference used for this observation date is available here:

https://okasinaikimono.blogspot.com/2025/07/0718f.html

## Record Summary

The strongest evidence from this survey indicates that a duckling that had become separated, survived predation affecting its group, and temporarily joined another brood later returned to its probable original family.

The same recording documents a duckling initiating a descent that its mother then followed, four young waiting calmly during a temporary maternal absence, peaceful movement among unrelated ducks, changing summer territories, and an unexplained regurgitation-like movement.

None of these observations alone establishes a general rule about Eastern Spot-billed Duck behavior. Together, however, they preserve details that may be useful to people searching for brood mixing, duckling adoption, family reunion, maternal absence, duckling waiting behavior, urban river ecology, and the development of wild duck families.


Timestamp Memo (For Personal Use)

00:00 Highlights (in no particular order)
03:01 Lots of ducks! Resting in the shade and swimming
It seems like many of the 70-day-old Af group are mixed in, but I couldn’t tell them apart, and I couldn’t spot Af mother either.
04:03 Lf4-50 Mixed in with the duck group, peaceful
If you can tell Lf mother apart, you're an expert! The ducklings also passed through normally, which is a pretty rare scene, but it's for enthusiasts.
06:57 Lf4 at the summer resting spot! Even the other ducks got chased away!
Today, I’m going to search for the Kf, Qf, and Cf groups that I couldn’t find yesterday. Especially Kf group, I’m really curious if they have 3 or 4 ducklings, so I want to find them if possible.
08:36 Kf2-7 back at the small water gate
It’s been there since yesterday. Normally, no duck families settle here, but it’s a bit exciting to find Kf here. It seems like it got carried away by the flooding and couldn’t return.
09:41 Duckling wants to go down, leading Kf mother
10:38 Mother wants to go up, leading the duckling
11:19 ★ Duckling wins! Jumps down the slope, and mother follows.
After jumping down, they swim very slowly, which is rare.
They go down the river, and although I was watching the usual route, by the time I realized, they had already passed through the reed thicket. For some reason, this year, none of the families are using this spot (last year, all the duck families gathered there).
15:30 Hooded crow couple? Rare to see them standing in the thicket. Are they sunbathing?
17:14 Close-up of a hooded crow’s face! So cute!
They then went under the bridge. I thought Kf2 might pass below, but I lost track of them.
17:56 Of2-47 Safe and sound. The ducklings are growing more robust.
Near the dam below. It’s a familiar family that often appears (they act similarly to last year’s pattern and took over the area where Mf was last year).
19:35 Mf1-50 Safe! It’s getting harder to tell them apart…
19:53 Ducklings running! (Mf mother flew away!)
20:42 Found them! Kf group… 4 ducklings!! After mixing with the surviving Kf, they are back with their real family!!
This was such a joy! The other day, the mother and three ducklings got separated and the surviving four mixed with Kf. Two got eaten, one disappeared, and the last one almost joined Kf mother but couldn’t. Miraculously, they blended in with Kf yesterday, and today, I could confirm there were four ducklings in the Kf group. The survival of the last duckling is now confirmed!
21:27 Kf4-7 Napping on a small island
If they’re sleeping here, it’s likely they settled in this area. This overlaps with where I saw Cf1 yesterday.
22:23 Duckling preening is so cute
I’m so happy to have met them, so I’ll just watch for a while.
28:41 ★ One duckling disappears behind the mother! I want to see all of them together…
29:28 Kf mother flies off, leaving the ducklings behind Quietly waiting, the ducklings
Bullfrog croaking. It’s becoming more common to hear them in this river (I didn’t hear them five years ago, and now I hear them frequently).
31:19 Duckling’s strange behavior, almost choking.
It’s similar to the behavior when kingfishers regurgitate pellets, but do ducks do that too? I’ve seen similar behavior but never seen them regurgitate.
40:22 Despite koi being nearby, the ducklings are calm.
One of them, the day before, had a duckling eaten right in front of me, but they might not know what happened. That feeding spot is usually a popular resting place, so even though it’s dangerous, they might have stayed there because they wanted to.
43:35 Kf mother is back! Reunited!
The ducklings noticed her before I could hear the splash of her landing.
44:01 Kf4 departs! It’s a beautiful day.
47:19 Kf mother takes over another duck’s resting spot A good summer spot under the bridge?
I then searched for Kf5 and Cf3 down the river but couldn’t find them. I didn’t find Hf2, Zf1, Cf1, or Uf1 either. I believe the Cf1 I saw yesterday is somewhere, but Kf4 might have moved in.
50:00 Kf4, this thicket is where ducklings like to go in (same situation as Cf1 yesterday).
51:56 A lot of young ducks in a popular resting spot! I confirmed seven ducks…
The day before, I saw Kf’s lost ducklings in the place where fish had eaten them.
53:30 Of2
Near the stream entrance. Didn’t see Sf2.
53:53 A heron near the duck’s resting place Peaceful, calm.
The day before, Ef6 strongly reacted and threatened the heron.
56:36 Lf4-50 Napping, only one duckling is active.
57:43 If4-46 Napping on the opposite bank.
Yesterday, Lf4 and If4’s resting places were swapped.
58:12 The shade under the bridge is very popular. A lot of ducks on both banks.
The duck at the front left is Cf mother! The ducklings seem to be separate from her now? I assume they’ve finished raising them. There were also some other females with distinctive feathers, but none matched.
1:00:01 Uf1-38 was in the breeding area!
There was one duckling I didn’t recognize. I thought it might be a surprise, and it turned out to be the mother too! They’ve settled in the breeding area since the other day and didn’t go up the water gate.
1:01:42 Tf8, split into 4,4 for napping.

Summary
The miracle of the Kf group’s ducklings being reunited after a tragic event. The ducks’ behavior has changed a lot this year, and I’m glad to see the Kf ducklings thriving. However, I couldn’t find the Kf5 and Cf3 groups, even though I searched hard for them. Tomorrow, I plan to check the upstream areas and hope to meet Ef5 and Xf5. If I can meet Ff6, Gf7, and Df5 after 60 days, I’ll be thrilled!

https://okasinaikimono.blogspot.com/2025/07/0718f.html