commonmoorhen

Who is Eating the Goslings?

The Question: We have a small pond (1 acre) with a small island in the middle. Every year we have a geese pair nest on it. The island is in the middle and about a 20 ft circumference. The pond is about 12 feet deep and stocked with bass, blue gill, and catfish. Muskrats live in the pond. The geese nest on the island. This year there were 8 hatchlings, 7 disappeared one day, the last one a few days later. No other predators I know of. An occasional fox passes through (rare), we occasionally see raccoons, and there are coyotes in the area. We have two large dogs who have the run of the place and this keeps down the fox/coyotes/raccoons, but they seem disinterested in the goslings. There are numerous red tail hawks in the area and vultures, as well as herons who like the pond. There are snakes in the area. We see them swimming in the pond occasionally and there are copperheads in the yard. The funny thing about this is that it seems to be a mass killing, which I think it must happen all at once. That would seem to rule out snakes. Seems funny for a hawk to get 7 in a day. I more imagined a raid on the nest, but on the island seems strange to me. Could the bass be getting the goslings?

Submitted by: John, Missouri, USA

The Short Answer: This is a murder mystery with a lot of suspects! Almost all of the creatures you mention are capable of taking goslings. Normally, an island would provide some protection from some of the more terrestrial predators, but this is a pretty small pond. I wouldn’t be surprised if a fox or a coyote would swim to the island if it knew there were a handful of gosling snacks waiting. Raccoons would also be high on the list of suspects, and Canada goose goslingthey certainly aren’t afraid of water. Hawks and even crows will take goslings from above, so the island is no protection from them. Neither would it be protection from a stalking heron. Snakes are also likely gosling predators, but as you say, they would be less likely to get a bunch of goslings in one day.

Of course, Canada goose parents will vigorously defend their goslings, so it would be difficult for any of these predators to get them all before the adults counterattacked or moved the goslings to safety.

One thing you didn’t mention is disease. Goslings are susceptible to disease, and that can often wipe out an entire clutch of goslings, in very little time. One deadly possibility is Leucocytozoon simondi, a protozoan blood parasite similar to malaria, which is carried by black flies. One documented outbreak of Leucocytozoonosis in Michigan killed 84% of goslings. That’s about the right level of mortality to match your 7 out of 8 missing goslings.

More information: I asked Tom Fondell, a Wildlife Biologist for the U.S. Geological Survey at the Alaska Science Center, for his opinion. Tom has done research on gosling mortality of the Canada Goose (Branta canadensis) at the Copper River Delta in Alaska. The list of predators there is different from that of central Missouri, but not as different as you might think. Here’s what Tom said:

“For most waterfowl the first few days are the most dangerous. In our study, on the Copper River Delta, the main predators of the goslings were mink Canada goose and goslingsand eagles.   Maybe mink could also be a problem in Missouri.  Muskrats would not be a problem.  Raccoons might take a gosling or two. But I would be surprised if the adults did not put up a defense against a small mammalian predator, and that the goslings would disappear all at once.

“In some ways predation by bass makes sense. The adults would not be able to defend against them, and might not even observe the predation event occur.  I worked on a canvasback project in Nevada (Ruby Lake National Wildlife Refuge) where the number one predator of ducks was suspected to be bass and these were just fish in the 1- 1.5 lb range.  (A study of bass there did find baby coots in the stomachs of a number of bass.)  If this guy has large bass (several lbs and larger) I do not see any reason they wouldn’t take goslings, especially during the first few days after hatch.  And if there are a number of bass in the pond I do not see why they wouldn’t take many goslings.”

Given Tom’s findings, mink strike me as a very good possibility. According to the Missouri Department of Conservation, mink are present throughout Missouri. But because they are small and mostly nocturnal, you might never see them. When I asked Tom about disease, he thought that was a possibility, but that you might have noticed sick goslings. I guess that depends on how closely you watch them. Tom’s suggestion is that you should make a gosling lure and see if you can get bass to strike at it. That might give you a clue as to whether bass are the culprits.

Another underwater suspect is snapping turtles, which will pluck baby waterfowl from underneath in shallow water. Unless there’s quite a few of them in the pond, it doesn’t seem likely they’d get them all so fast, however.

Of course, one simple explanation is “all of the above.” It’s possible that it isn’t really one predator taking seven goslings at one time, it just happened to seem that way. With so many dangers in such a concentrated area, it doesn’t seem out of the question to me that you could easily lose one gosling to seven different predators in a single day. Tom Fondell also pointed out that if there isn’t much forage for the goslings on the little island, the parents may be leading them far afield, exposing them to predation from everything from the bass to hawks.

One Suspect We Can Rule Out: Goose parents don’t seem to count that well … or maybe they do. On larger bodies of water, where there might be more than one pair of geese breeding, the goslings often get mixed, and the parents don’t always seem to sort them out. One day, you might have two pairs, each of which has five goslings (about the average). And then the next day, you see one pair has only one gosling. You might think they had a disaster, but then you realize the other pair all of a sudden has nine goslings. Is that because goose parents can’t count? Or maybe they’re perfectly happy to have someone else do the work of leading their goslings around.

In this case, however, with only one pair on this small pond, we can probably rule out gosling mix-ups.

Sources:

Stolley, D.S., Bissonette, J.A., and Kadlec, J.A. (1999). Limitations on Canada goose production at Fish Springs National Wildlife Refuge. Great Basin Naturalist 59(3) (1999):245-252.

Herman, C.M., Barrow, J.H., Tarshis, I.B. (1975). Leucocytozoonosis in Canada geese at the Seney National Wildlife Refuge. Journal of Wildlife Diseases. 11 (1975):404-411.

Fondell, T, Grand, J, Miller, D, et al. (2008). Predators of dusky Canada goose goslings and the effect of transmitters on gosling survival. Journal of Field Ornithology, 79(4), 399-407.

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16 Responses

  1. John Says:

    Thanks very much – your discussion was very interesting and enlightening. Guess we’ll keep an eye out for mink.

    Thanks again.

    John

  2. Tom Says:

    You’re welcome. Let me know if you see any mink. I’d try the “crepuscular” hours, the hour just before sunset and just after sunrise. That’s when you’re most likely to see a mink patrolling the pond shoreline, maybe.

    Also, Tom Fondell, the USGS biologist, is very curious to know the results if you ever try to make a gosling lure.

  3. David Says:

    This is interesting. We have the exact same situation here on our pond in Colorado. Two nights ago we had six goslings and then the next morning there were none. We had observed them for about 10 days and they were doing fine — along with two other goose families of two and three goslings. We have fox, Herron, eagles, and mountain lions around here but it seems so odd that they all disappeared in one night. It seems like the parents are wandering around somewhat lost..

    I would really like to figure out the mystery..

  4. David R. Says:

    We have watched a pair of geese for 8 years trying to successfully raise a family. Most never lasted the day much less a week. Last year we had a temperature inversion in our 2 acre lake that killed all of the fish. This year the Geese had 8 goslings, the largest ever. So we suspect the fish were eating them as some of them were very large. They had their habits of where they went during the day. We had an area that we fed them cracked corn. Everything looked good on the morning of day 23, but that night they were gone. We have not seen them since, do you have any ideas? Our property is about 2 miles from the Illinois River and did not know if they would make the long trek to get to it.

  5. Tom Says:

    Are you saying that the whole family was gone, adults included?

  6. David R. Says:

    Yes. Absolutely no sign of any kind of fowl play. Just one morning they are here and that afternoon they are gone. I have about 8 acres with a 2 acre lake and a small pond. They had a routine of where they went and when so I knew where to find them at any time. Last year they had 3 surviving goslings after 2 weeks. A week later it was down to one and then they were gone. But the next year the same couple will be back. I knew it has been the same as they knew where I place the feed on the property. They go to that spot and will wait for me to come out and place it on the ground.

  7. Tom Says:

    David from Colorado, you mention other pairs of geese. Have you counted the other goslings to confirm that yours haven’t just switched parents as they sometimes do?

  8. Jess Says:

    I read your response to the person who inquired about their missing goslings every year. I am in Boston, and here, was watching some canadian geese raise 6 goslings for about 3-4 weeks. They were already quite large, and living in a small sanctuary surrounded by suburb and city development, so no snakes or foxes here.

    Every day people would go out to see the goslings, and they seemed quite safe with aggressive parents, and were fairly enclosed inside this mostly gated nature sanctuary. Recently, all of them disappeared, including the parents. One day, the family was there, the next, gone.
    Do you have any idea what could have happened? Could all of these birds, even with their large size at this point, have been predated all at once? I saw no evidence of feathers anywhere.

    The goslings did not yet have flight feathers, but were about 3-4 weeks old. I am going to check with the town to see if there was any human interference, but I doubt it, given that it’s a sanctuary and people have been watching them actively. What could have happened to them? Could they simply have walked away from the area? We are all very worried around here and feel quite protective of these geese.

    Thank you!

  9. Tom Says:

    Wow. All these missing goslings! It’s hard to imagine, based on these reports, how it is that Canada goose populations are so high. I think it’s unlikely in each of these new cases that the goslings and parents were all predated in one night. I think it’s more likely that in each case, they moved off in search of greener pastures. However, I’ve sent off an email to our goose predation expert, Tom Fondell, to see what he thinks. Stay tuned.

  10. Tom Says:

    It’s obviously impossible to know what happened in any of these cases, without on the scene evidence, but here are some things to think about:

    1. Goslings often get mixed up between adults. If you have several pairs all with goslings, check to see if the other pairs suddenly have more goslings.
    2. It would be a mistake to assume there aren’t predators, even in a gated sanctuary. Foxes and even coyotes have become quite habituated to people and are frequently found in city parks and backyards. And of course, the slithering and the aerial predators aren’t generally bothered by fences. However, it would be unusual for a whole clutch of goslings to disappear overnight as in all these cases.
    3. It seems to me that disease is the only cause of mortality likely to take a whole clutch at once. And disease can move fast. It’s not unusual for young birds to be fine one day and dead the next.
    4. Parents who have lost their entire clutch to predation or disease are likely to move on and try somewhere else — leaving the impression that the entire family was killed.

    With those other possibilities in mind, I think it’s most likely that in all three of these cases, in Boston, Colorado and Illinois, the parents and goslings decided the grass was literally greener somewhere else and moved out overnight (they eat grass, don’t forget). Tom Fondell, USGS wildlife biologist and expert on goose mortality says: “Much of the muscle mass in newly hatched goslings is in their legs, and once the down is dry the goslings are ready to move. Geese can move miles with their goslings, usually doing a little at a time (if going long distances it may take several weeks) and typically they are faithful to the same ‘brood rearing’ areas, and show they same movement pattern between years. But if disturbed they can move more quickly.” The parents may have decided that one place was good for a nest, and another place is best for raising the goslings to adulthood.

    So it seems most likely that your geese families have simply moved on. Wish them luck!

    One question for all three locations: was anything done to the grass near the water? Spraying, fertilizing, mowing, etc. that might have convinced the parents that it was no longer palatable or safe? That might have triggered the geese to move on.

  11. Jess Says:

    Thank you!
    I will check out what the town does there in terms of grass treatment. Hopefully nothing. :) And I certainly hope they have moved to greener pastures! Did he say it was common, given the strong legs, for the whole family to do that mid-fledge?
    Thanks!

  12. Dave Says:

    Thanks a great deal for your help Tom. Based on what I have read I will go with the story they simply moved on down to the river. Now I get to watch the deer and turkeys eat the corn that I used to leave out for the geese.
    Living in the country has it’s advantages and enjoying Mother Nature is one of them..

  13. Joe Says:

    Just FYI, I recently returned from our property in the U.P. of MI. We have several ponds with bank edges that are mowed at times. This Spring we had at least 6+ or so Canadian goose pairs nesting. In later spring they had the goslings in tow. Now there are about zero around. I only saw a few transient adult geese.

    I did see some older droppings and many locations on the dam/dike/bank with a pile of adult goose feathers. This would be where something ate an adult goose. The goslings were gone without evidence.

    The goose was killed or consumed on the top of the bank, not near the waters edge. Any leftovers may of been carried off. I know adult geese are very protective of their young & would stay around trying to protect them.

    There is about every predator present in MI on this remote U.P. location. It would be nice to have a successful nesting or 2 of the pairs that started out. Our main suspects for the babies and maybe adults are bald eagles,coyotes, and large hawks(red tail), though I wouldn’t rule out bobcats & even wolves trying a few. We have only seen the eagles and hawks present, & tracks of the rest. There are no fox around this location.

    A friend on mine did observe a coyote take several goslings in a group on his WI property.

    I did see a female wood duck with one baby left. I also saw a fawn leg with a scattering of wolf tracks around. I feel due to various reasons the system is tilted in favor of predators.

  14. Lisa Says:

    This is fascinating…we have a spring fed bog just off our backyard, and the same geese pair have been nesting on it for two years, on top of muskrat huts.

    Both years she hatched 7 and 6 goslings, respectively, and the same thing happened to all of them on the 2nd or 3rd day after hatching: the pair left in the morning with all of them in tow and a few hours later, they returned with none. The adults cried and cried last year (it was quite horrid!), as they went back and forth to the nest and circled around the edges of the bog, looking for the goslings.

    I’ve been wondering what happened that would make all of them disappear at once. I’ve never heard a fight or anything from the adults, as they usually go to a pond that’s adjacent to the bog where they nest (so I’d hear them if there was a commotion). It’s like they think they’re returning with the goslings and suddenly have no idea where they are.

    I’ve heard a few people say there are bass in the adjacent pond, and now I think I’ve possibly solved the mystery…especially since you said that often the adults don’t even know they go missing. It’s a sad thought, but at least we know!

  15. David Everest Says:

    Ww have a large pond here in Northern California and each year we get a few geese that land here and hatch goslings on the small island in the middle of the lake. They are fine for a week or so and then all the goslings disappear overnite. We suspected all kinds of different predators but now we have singled out our bullfrogs from the list of usual suspects. One of the older children who was swimming in the pond actually saw a bullfrog take down a gosling and was horrified by the sight. We feel like we have solved the mystery of the gosling serial killer. The only question is why they all disappear at once.

  16. Nelson Says:

    We have the same problem every year. We live in the NYC suburbs, Northern Westchester. We have a 1.25 acre pond. Each year we have a set of geese that hatch goslings. We assume they are the same ones every year but it’s hard to tell. Sometime mid morning Between 8 AM – Noon we lost 3 of the 7 goslings. We do have large bass in our pond, also large snapping turtles and bull frogs. Red Tailed hawks, eagles and Blue Heron are in the area as well as fox and coyote. We have dogs so many of those predators are scarce on our property. I suspect the bass and the snapping turtles.

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