DURING the summer there are several thousand ducks in Yellowstone. In August 1938 more than 200 ducks were on the open waters of Swan Lake and many others may have been out of sight in the vegetation. In another instance I saw more than a thousand on a single lake. Some of the species included in the summer population are: mallard, Barrow's golden-eye, American merganser, gadwall, blue-winged teal, green-winged teal, and harlequin duck. During the spring and fall numerous other species also stop on park waters.
Many ducks winter on the open waters. A count made between January 14 and 20, 1939, resulted in the following: mallard, 316; goldeneye (American and Barrow's), 556; merganser, 73; bufflehead, 78; and green-winged teal, 10. In addition, 241 Canada geese and 106 trumpeter swans were counted, making a total of 1,725 waterfowl. A similar count made in the winter of 1938 yielded a total waterfowl count of 1,618. These counts are incomplete but are roughly comparable. They at least indicate that there are many ducks wintering in Yellowstone.
The majority of the 5,086 coyote droppings were collected in areas where ducks were plentiful during the nesting season and could be expected to furnish an appreciable amount of coyote food. Special effort was made to obtain representative collections in the vicinity of duck nesting localities.
Of the 5,086 coyote droppings collected duck remains were present in 82, or 1.6 percent. The incidence of occurrence was about the same in the 2 years during which droppings were gathered. In addition to the foregoing 18 food items classified simply as "large bird" and 62 as "bird" may have included some duck remains, not recognizable as such. The remains of 11 of the ducks were recognized as those of mallard. Furthermore the following feather remains, in spots where ducks had been eaten, were found along the Firehole, Yellowstone, Madison, and Pelican Rivers: 13 unidentified ducks, 6 mallards, 3 green-winged teals, 1 gadwall, 1 bufflehead, and 1 goldeneye. These remains were found along about 40 miles of river banks and lake shores.
Evidence of duck nest raiding was very meager. Eggshell fragments, possibly those of ducks, were present in 10 droppings and a single duckling was present.
Droppings containing duck feathers were sometimes grouped near feather remains in one spot, suggesting that a single duck was represented in several droppings. As an example, at one such pile of feathers were three fresh coyote droppings, all containing duck remains. The following is also suggestive: On December 17, 1937, on the bank of Flat Creek in Jackson Hole, I found the carcass of a female mallard which a coyote had investigated. Pin feathers on the wing showed that the duck had died in late summer during the moult. Only a little of the breast was eaten. The coyote had gnawed lightly at the dried carcass, then left it. Two or three feathers in the coyote's trail 10 feet away probably had dropped from his lips. Judging from other observations it is possible that subsequently, each time the animal passed that way, it nibbled at the bird enough to swallow a few feathers, thus leaving feather records in several droppings.
An unknown proportion of the duck remains would represent carrion. Near several of the better duck waters are telephone wires which the ducks probably fly into occasionally and thus lose their lives or become severely injured. As mentioned elsewhere, several dead grouse were found which had flown into the buffalo pasture fence and a telephone wire. A robin had been killed flying into the same fence, and one evening, in the dusk, one of two robins struck the single telephone wire and fell to the ground with a thud. Since even bats do not always avoid objects, such as nets it seems probable that a swift flying flock of ducks might occasionally lose a member in this manner.
In the autumn, wounded or sick ducks apparently come into the park and are unable to leave, either dying or remaining on the waters in a flightless condition. Such ailing ducks would occasionally fall prey to coyotes or furnish a certain amount of carrion. Concerning wounded ducks, Assistant Chief Ranger Albert E. Elliott, (Yellowstone Nature Notes, January, 1937, p. 7) writes:
Kalmbach and Coburn (1937) found disability and mortality among ducks wintering in southern Idaho in 1937 and report that such mortality on wintering grounds is not unusual. Inspection of 2-1/2 miles of banks of the Portneuf River near Pocatello disclosed 75 dead ducks, and a number of dead ducks were found along several drainage ditches. These ducks were heavily parasitized and lead shot was present in some of the birds. In view of these findings it is not surprising that disabled birds are found in Yellowstone.
An interesting though probably a minor cause of duck carrion is mentioned by N. P. Langford (1870). He writes:
The extent of this kind of mortality is probably not great, and probably those scalded but still able to get away would be available to the coyotes. In the hot pools of Old Faithful I have seen duck and goose skeletons. Near a hot pool at Old Faithful in which lay the skeleton of a duck, Assistant Park Naturalist W. E. Kearns found a coyote dropping containing duck feathers; however, there was probably no connection in this case between the duck remains in the spring and the feathers in the dropping.
During the summer of 1937 I found the carcasses of three mallards and a merganser that had not been eaten, the carcass of a mallard that had been partially eaten by birds, and two complete skeletons of uneaten ducks. These seven carcasses, undiscovered by coyotes, suggests that there must be many others that they do find. During the fall the amount of duck carrion would probably be greater than during the summer because of the influx into the park of injured or sick ducks.
In the interpretation of field observations it should be kept in mind that other animals besides the coyote are potential predators on ducks. Mink and otter probably occasionally catch one, and the eagles, of both species, prey on ducks to some extent, I once saw what appeared to be a golden eagle in immature plumage sitting on a mallard not yet dead. At Old Faithful in April 1938 I found the wing of a bufflehead duck at the base of a telephone pole and a bird pellet containing duck feathers at the base of an adjoining pole. The duck may have been killed by a predator, or it may have flown into the wires and died from injuries. In the same region about a mile away another bird pellet was found containing duck feathers, and at Gibbon Meadows in the spring of 1937 two bird pellets contained duck feathers. I mention these other predators here to show that preying on ducks is distributed among a number of species, including the coyote.
During the winter of 193738 from 40 to 50 mallards and about as many goldeneye ducks spent the winter on 3 or 4 miles of the Gardiner River where coyotes were concentrated. Frequently I followed the shores of the river during the winter in search of duck remains but found none. Coyotes were apparently not molesting these ducks. A few ducks winter on the Yellowstone River between Gardiner and Tower Falls but no indication of predation was found along this stretch of water.
Rangers report some duck predation by coyotes in winter but from all I can gather this is not serious. Coyote trails are frequently found along the open water but these animals would probably follow water courses in their travels if ducks were entirely absent, for streams are natural highways for many species. One such trail was reported to me and an informant conjectured that probably the coyotes were here persistently hunting the ducks in the stream. I investigated, picked up a dozen droppings along the beaten trail, and found that they all contained elk hair.
In late November 1938 I saw a pair of mallards on a bit of open water, not more than 7 or 8 yards in diameter, in an ice-covered lake near Blacktail Deer Creek. Once they flew off but returned to the water after making a wide circle. They were restless and apparently dissatisfied with the size of the opening. When a coyote came trotting toward them on his way to some carrion they flew away while he was still about 70 yards from them, thus indicating their alertness and feeling of insecurity.
I do not doubt that a coyote would seize a duck if he had a chance, but it appears that this opportunity occurs so seldom that both the birds and the coyotes usually ignore each other, especially when the birds have the advantage, as they generally do. O. J. Murie in his notes for January 25, 1939, in Jackson, Wyo., writes:
Such observations are quite typical of the relationship existing between ducks and coyotes.