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Field Notes - Bird Piracy Observations (Dec 9, 2007)
   

Piracy, in birds and humans, describes the act of one stealing from the other. In the bird's case, the item being stolen is food and not gold. Piracy is commonly associated with jaegers and gulls. They often chase and harass other birds to make them drop the fish they caught in the ocean or the hamburger bun salvaged from the McDonald's parking lot. Sometimes it is more energy efficient to steal another birds's meal than to try and catch or find their own.

I have a few observations of this activity that are worth sharing.

It is noted in several publications that some waterfowl partake in piracy. I have also observed this regularly myself at Cheam Lake Wetlands Regional Park. I have noticed that American Coots and American Wigeon like to hang out among the large rafts of diving duck species, which most commonly include Ring-billed Ducks and Lesser Scaups. When these divers return to the surface with aquatic plants in their bills, often there is a wigeon or coot waiting to snatch it away before the rightful owner can eat it themselves. Since these plants are certainly out of reach for the wigeon and possibly even for the coots, this is the only way to obtain this food source aside from picking up scraps, which also is a common sight among these feeding flocks.

Red-tailed Hawk vs. Sharp-shinned Hawk

Piracy among raptors is also well documented. Peregrine Falcons and especially Bald Eagles are the species I've personally seen stealing the prey from other raptors (including their own species). However, I was surprised to see a raptor species slightly out of its usual hunting habitat involved in a blatant act of piracy. During a walk at Island 22 Regional Park in early December of this month, I briefly heard the pitiful cries of a small bird being captured among the trees further ahead. As I came closer I watched closely to see if the predator would show itself. Sure enough, a Sharp-shinned Hawk juvenile emerged from the undergrowth with a now dead small bird in its talons. I had barely the chance to see the little hawk when an adult Red-tailed Hawk blasted in from above straight at the little Sharp-shinned Hawk. I surmise that the Red-tailed Hawk was attracted to the area by the sounds of the little bird in distress. The Red-tailed Hawk displayed excellent skills keeping up with the quicker and more agile Sharp-shinned Hawk as they twisted through the trees about 20 feet above the ground. After about three seconds, the Sharp-shinned Hawk dropped its prey and landed nearby. The Red-tailed Hawk immediately abandoned the pursuit and dropped down into the undergrowth after the abandoned bird, removing my original thought that the Sharp-shinned Hawk was the intended meal. Sure enough a few seconds later, the Red-tailed Hawk appeared with the small bird in its talons and went on its merry way flying past where the Sharp-shinned Hawk had landed and was possibly hoping to recover its meal.

I've never seen this occur before but wonder if it is slightly more common. The Sharp-shinned Hawk, upon giving up its meal, immediately ceased all evasive maneuvers and landed on a branch very close to where it dropped the small bird. There was no sign of fear even when the Red-tail flew away near where it was perched. There did seem to be a feeling of familiarity considering the small hawk could easily be a meal for the larger hawk. Just as we are usually able to read other people's body language, I feel without a doubt that the same is seen among birds. The Sharp-shinned seemed to know what the Red-tail was up to before, during and after their encounter and acted accordingly.

Getting a little off track with 'body language' among birds here, but a little side note of interest that may relate to the above observation. I've watched large flocks of ducks feeding in semi-flooded fields in areas that have many Bald Eagles flying back and forth. Most of the time, the Bald Eagles fly past and the ducks pay little to no attention to the eagles. This is even though the eagle could quickly stoop down on the ducks at any moment. Once in a while however, I will see the ducks suddenly get agitated. My scanning for predators such as a falcons only brings up another Bald Eagle flying towards us, and, to my eyes, doing the same thing as the first dozen eagles did. Sure enough, this eagle will suddenly make an attack on the ducks who are usually by this time already in the air. Somehow they know and can see something we cannot.

Pirating Pelican?

The most surprising piracy observation I have to share took place at Cheam Lake Wetlands Park on September 4, 2004. The night before, an adult American White Pelican was reported on the lake. The next rainy morning, I stopped for a look. Not long into the observation I saw an Osprey diving in the lake, presumably after a fish. As the Osprey hit the water, the pelican flew directly to where the Osprey was. The Osprey, with empty talons, retreated quickly from the large white bird with massive bill flying towards him. The pelican landed where the Osprey had been and probed around for a few seconds in the water with its bill. Soon after, the Osprey went into a hover a good 200 metres away, which usually indicates that a dive after a fish is soon to follow. The pelican clearly took note of this and started to fly towards the area the Osprey was hovering over. Several times this happened with the Osprey hovering and the pelican either showing interest or even taking flight in the direction of the Osprey. When the Osprey stopped hovering, the pelican would immediately land. The pelican showed no interest in the Osprey as it flew around the lake even when it flew close to the pelican. Finally, the Osprey hovered and dove again into the water. By the time the pelican made it to where the Osprey was, the Osprey had already taken flight. It was difficult to tell if the Osprey had caught anything thanks to the rain, mist and low light levels, but the pelican followed the Osprey briefly through the air before abandoning the short chase and landing on the lake again. The Osprey continued flying away from me towards the trees that contained a nest that was used that summer. The Osprey may have been carrying a fish but it was hard to be certain.

This certainly appeared to be a case of the pelican looking to rob an Osprey of fish. Osprey would be common in the area where American White Pelicans breed so there is ample opportunity for the two species to coexist in B.C. if not also on their wintering grounds to the south. I have learned that Ospreys are subject to piracy from Bald Eagles and Frigatebirds so it does happen. The other thought I had was that the pelican might have taken the Osprey as a threat. This is doubtful considering there are no young to protect and the Osprey was minding its own business at all times. The pelican only interacted with the Osprey when it showed signs that a catch may be imminent. There were several opportunities for the pelican to go after the Osprey when it was simply flying around, it did not do so.

It is certainly worthwhile to see if further behaviours of this type are noted in the future. I would be most interested to hear of more field observations of pelicans pirating fish from Ospreys. I'd love to know how they could get a fish from an Osprey or ever think that they could persuade a much faster and more agile bird to drop its meal. However, if piracy was indeed what was happening on Sept 4 of 2004, this bird must have had success with it in the past or it wouldn't bother trying to engage in an energy wasting exercise that has no potential for food to reward the effort.

From field notes of G. Gadsden 2004 - 2007

Links and sources:
Ehrlich, Dobkin and Wheye, (1988)

 

 
           
                 
 
                 

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