NOTES

merlin chases passerines
flushed by NortHERN HARRIER
Scott McConnell, P. O. Box 572, Haddonfield, New Jersey 08033;
scott.mcconnell1@yahoo.com
On 27 October 2009, 25 km east of Chugwater, Platte County, Wyoming, I spotted a male Northern Harrier (Circus cyaneus) approximately 900 m away hunting ata height of 1–2 m over a pasture. As it flew, the harrier frequently flushed passerine
birds, which it did not pursue. After approximately 30 seconds, the harrier suddenly
turned 180° and flew east at a faster rate of speed. I then noticed a Merlin (Falcocolumbarius) that had come in from the west and was now close to the harrier. TheMerlin began following approximately 5–10 m behind the harrier and using it as abeater, chasing the passerines being flushed by the larger raptor, which had resumed
its slower hunting speed.
I watched the two raptors for approximately 3–4 minutes, during which time thebirds were at least 600 m away from me. The Merlin followed the harrier for mostof that time and chased, but did not catch, passerines flushed by the harrier approximately 6–9 times. On two occasions the Merlin chased a flushed passerine up
to about 10–15 m above ground level but did not catch it and resumed following theharrier. Another time the Merlin raced back and forth several times along a low area
for approximately 15 seconds in pursuit of a passerine, then turned away and caught
up with the harrier again and continued to follow it. After 3–4 minutes the Northern
Harrier flew out of my view, followed by the Merlin. The harrier had, since the time
I first noticed the Merlin, flown approximately 1.25 km, including two sharp changesof direction. During that time I did not observe the Merlin behave aggressively toward
the harrier. Similarly, other than possibly its initial 180° turn at the beginning of myobservation, I did not observe the harrier respond to the Merlin.
Similar behavior between these species has been reported, though not frommainland North America. In the Bahamas, Van Tyne and Mayfield (1952) saw aMerlin following a harrier in a fashion similar to that I describe on three dates, butthey did not note that the Merlin(s) chased flushed prey. Dickson (1984) reported
seeing the behavior eight times in Ireland with these two species, and also recordedthat two other observers had seen it an unspecified number of times. Watson (1977)
reported seeing it on one occasion in England. Cudworth and Massingham (1986)
noted one instance of a somewhat similar interaction in England, and also noted thatthe harrier did not react to the Merlin’s presence. No prey captures by the Merlinwere reported for any of these observations in the British Isles, but Kenyon (1942)
reported several Merlins following a train in Mexico and capturing passerines thatwere flushed by the train.
The harrier’s active hunting style, slow flight, and habit of continually flushing passerines seems to present a situation faorable for hunting for a quick, opportunistic
Merlin. Harriers that I have watched in Wyoming invariably flush passerines as they
fly low over a field, but they do not pursue the flushed birds—they ignore them andinstead attack prey still on the ground (also see Cudworth and Massingham 1986).
And with the Merlin trailing the harrier, the latter would encounter potential prey first.
The harrier, then, appears to be unaffected by the tailgating Merlin, which suggests
a commensal relationship if the Merlin is in fact successful at obtaining prey by thisstrategy.
Lawrence Semo, Paul Swiby, and Doug Faulkner made serveral suggestions toimprove the manuscript.

Western Birds 42:49–50, 201149

NOTES
Literature cited
Cudworth, J., and Massingham, C. 1986. Hen Harrier and Merlin hunting together.
Br. Birds 79:430.
Dickson, R.C. 1984. Falcons hunting close to harriers. Br. Birds 77:481–482.
Kenyon, K.W. 1942. Hunting strategy of Pigeon Hawks. Auk 59:443–444.
Van Tyne, J., and Mayfield, H. 1952. Bird records from New Providence and Eleuthera
Islands, Bahamas. Occ. Papers Mus. Zool. Univ. Mich. 538:1–4.
Watson, D. 1977. The Hen Harrier. T & A. D. Poyser, Berkhamsted, England.
Accepted 4 January 2011

Merlin50

Sketch by George C. West