Tag Archive | swainson’s hawk

Goldfinch and Other Backyard Birds

Posted by Bob Lefebvre

The first American Goldfinch of the year arrived in our yard on Mother’s Day.

American Goldfinch (male), Calgary, May 14, 2017. Photo by Bob Lefebvre.

American Goldfinch (male), Calgary, May 14, 2017. Photo by Bob Lefebvre.

Although I occasionally hear goldfinches flying over in the summer, they don’t stay to breed in my neighbourhood and I usually don’t see them in my yard except on spring and fall migration.

There are Northern Flickers here year-round, and there are at least a couple that are still courting, so maybe this is the year that my Flicker nest box finally get used (by Flickers, rather than House Sparrow, Starlings, or squirrels).

Northern Flicker (intergrade male), Calgary, May 16, 2017. Photo by Bob Lefebvre.

Northern Flicker (intergrade male), Calgary, May 16, 2017. Photo by Bob Lefebvre.

This year our local pair of Swainson’s Hawks is building a nest just down the block, so I’m seeing and hearing a lot of them. I will post more about these birds as the season goes along.

Swainson’s Hawk, Calgary, April 30, 2017. Photo by Bob Lefebvre.

Sunday Showcase: Summer in Alberta, Part 4

More summer bird photos from Tony LePrieur, taken in and around Calgary, except for the Western Kingbirds, which were near Brooks in SE Alberta.


Horned Grebe with chick.


Tennessee Warbler.


Tennessee Warbler.


White-throated Sparrow.


Western Kingbird (adult).


Western Kingbird (very young bird, just fledged).


Warbling Vireo.


Savannah Sparrow.


Song Sparrow.


Swainson’s Hawk.

Update on Swainson’s Hawk Chicks

Posted by Bob Lefebvre

Here are some more photographs, taken by Colin Nakahara, of the Swainson’s Hawk and chicks at a nest in SE Calgary. This post from last week showed the downy young in the nest. Today’s photos, taken on July 14, 21, and 29, show the growing chicks. Unfortunately one chick didn’t make it.

All photos by Colin Nakahara.

July 14 (1)

Adult Swainson’s Hawk (left) and young in the nest. July 14, 2016.

July 14 (3)

July 14, 2016.

July 14 (13)

The adult hawk, keeping an eye on Colin but appearing calm.

July 21 (23)

July 21. Another week older, and a little closer to leaving the nest.

July 21 (28)

July 21.

July 29 (3)

July 29 – adult.

July 29 (13)

July 29 – one of the chicks.

July 29 (11)

This one looks just about ready to fly. July 29.

Terry’s Travels: Birding the Stavely Area

Hello; allow me to introduce myself. My name is Terry Korolyk. I have been, among other things, the Compiler of the City of Calgary and Nature Calgary Bird Alert since 1994 and have  also been  the Compiler for Alberta for the Prairie Provinces Region of North American Birds, a quarterly publication of the American Birding Association, for approximately 16 years.

Currently, I am working on 2 birding books with one being “The Birds of the Calgary Area and Southern Alberta”, and, the other being the “The Birds of Fish Creek PP”. I am sure most of you are well aware of how well known Fish Creek PP is in our area as the Park is often featured on Birds Calgary.

I will be contributing on a regular basis to the Blog with my first venture focusing on a trip I led for Nature Calgary Saturday, July 16 down to the Stavely area to bird concentrating on the huge Pine Coulee Reservoir west of Stavely and Clear Lake on the prairie 15 km east of Stavely on Township Roads 140 and 142. From the main parking lot in the Glennfield area on the east side of Fish Creek PP, we cruised down Highway 2 as far as Nanton turning off and following the road behind the Esso (Regular Unleaded is almost always 2 cents more than the other Gas Stations in the town at the Esso) directly to the south end of Nanton. This road is usually quite birdy and is almost always a sure bet for one, if not more, EURASIAN COLLARED DOVES.

Sure enough, we did see one perched on a telephone line.

Once at the south end of town, we crossed the highway and set out for Pine Coulee Reservoir. This road is paved much of the way, but, just as the pavement ends, a fairly large slough appears from just over a hump. Usually, this is a good birding stop on the way, but, given the recent rains we’ve had, the slough was flooded and not one bird was present. We pushed on. Following a few kilometres of gravel, we reached Township Road 150 and made the turn left to descend down the switchback to the reservoir. To this point, the drive from Nanton was very birdy with lots of Buteos (mostly Swainson’s Hawks, but, in a different variety of plumages. Vesper and Savannah Sparrows and Western Meadowlarks, all singing, had lined our route.

The mudflats were extensive on the south of Township Road 150 where it crossed the north end of the reservoir. Large numbers of shorebirds from the North prodded and poked about in the muck. A few minutes birding there produced 250+ Lesser Yellowlegs; 60 Baird’s Sandpipers, and, 1 Stilt Sandpiper amongst many Killdeer. Female Ducks of different species led their broods of tiny Ducklings almost everywhere on the water on both sides of the road. Flocks of Tree and Bank Swallows and 2 resident Cliff Swallows swiveled back and forth the over the water in search of flying insects. There were many juveniles as it had become fledging time for them.


Juvenile Bank Swallow.


Adult Bank Swallows.

We carried on soon ending up at the Dam, which, in Fall is a great landfall for migrant waterfowl and other birds heading to their wintering grounds. At this time of year, there was an assortment of Diving Ducks and other birds which included 1 immature Double-crested Cormorant, and, 3 juvenile BARROW’S GOLDENEYE.


Western Kingbird.

Leaving the Dam on Township Road 140, we found more waterfowl and both Western and Eastern Kingbirds started to show themselves. Mourning Doves also started to appear. We turned right on Range Road 281–more Mourning Doves; 7 of them.


Mourning Doves.

Almost immediately after, one of the prizes of the day, a pair of COMMON NIGHTHAWKS, a male and a female, bounced around in the air against a backdrop of billowing white Cumulus clouds, and…………at the same time!……….a FERRUGINOUS HAWK soared against the clouds. We then stopped for lunch a few hundred metres along at a slough that, in past years, was an excellent location to observe American Wigeon during breeding season. Spring migration periods at this slough produced large numbers of Wigeons usually including one or more EURASIAN WIGEONS and EURASIAN-AMERICAN males. I could recall one particularly spectacular looking individual of this hybrid. This year, however, Eared Grebes, colonial birds, were nesting there, and you could see their many vegetation nests jutting above the water’s surface. Flocks of Brewer’s Blackbirds, Brown-headed Cowbirds, and, European Starlings horded along the water’s edge and in in the nearby crop fields. We headed back to Township Road 140 and then headed east to Clear Lake.


Swainson’s Hawk.

There were more Mourning Doves then, and, both Swainson’s and Red-tailed Hawks on the drive to Clear Lake, then  after we crossed Highway 2, Horned Larks started to appear along with the Vesper and Savannah Sparrows. The Campground at Clear Lake gave us great chances to observe both Western and Eastern Kingbirds again. On the lake, Eared Grebes and Franklin’s Gulls loafed and hunted respectively, but…………amongst all the Franklin’s Gulls swam 1 breeding-plumaged BONAPARTE’S GULL, a nice surprise and a chance to watch a bird we don’t see much of here at this time of year.

Heading north on Range Road 261 up the west flank of the lake we found an adult FERRUGINOUS HAWK perched on a fencepost. Birds seen at the north end of Clear Lake included 10 breeding-plumaged SHORT-BILLED DOWITCHERS while a Mammal sighting there included one very large White-tailed Deer doe crossing the lake.


Ferruginous Hawk.

We headed north on Range Road 260 to start the return trip to Calgary. We had time for 2 very good stops—-one at Township Road 152 and Range Road 265 where we watched many fledging and adult Tree, Bank, and, Cliff Swallows, and, the other on the west side of Range Road 270 just south of Highway 533  where we found 19 migrating RED-NECKED PHALAROPES in breeding plumage swimming on the water along with 3 more SHORT-BILLED DOWITCHERS along the shoreline. Amongst the duck species there was 1 hybrid female GADWALL-NORTHERN PINTAIL! Our final bird of the day was a bird I think is one of our showiest and most flamboyant on Range Road 272 south of Highway 23:


Loggerhead Shrike.

We reached Highway 23; turned north on Highway 799 and followed that and Highway 552 and Dunbow Road back to Calgary.

For those of you who do not know what Bird Alerts do (they are also known as RBAs, or, Rare Bird Alerts ), they are a phone service used to report sightings of rare and unusual birds. In our case here in Alberta, the city of Calgary RBA number is 403-221-4519. If you have found a rare or unusual bird, or, have noticed some unusual interesting bird behaviour, or, have noticed an unusually large number of individuals of a particular species of bird, or, have noticed a bird in the province here out of season; by all means, report it. Anything you think relevant to any of the already mentioned requirements, go ahead and report it to us.

If you phone to report anything, I will have compiled a message which you can listen to, or, if you just want to leave your information, you may do so after the beep. Information should consist of the bird(s); location of the sighting (be as specific as possible using Route numbers; distances from prominent landmarks, etc.); date, including time if possible, and, a telephone number where you can be reached. I collect all the messages and record a new RBA every Monday and Thursday evening with all the information that has been deposited and the process repeats itself.

Nature Calgary field trips are free and open to anyone. See the list of upcoming trips here.

Sunday Showcase: Swainson’s Hawk Chicks

Posted by Bob Lefebvre

Swainson’s Hawks commonly nest right in the city, but since the nests are high in the treetops it is usually difficult to see the young birds before they fledge. Here are some photos taken from the rooftop of a business in the Highfield industrial area of Calgary. They were sent to me by Mark Dann, and the photographer is Colin Nakahara.

June 28 (9)

June 28, 2016: Downy Swainson’s Hawks chicks in the nest. Photo by Colin Nakahara.

July 7 (24)

July 7, 2016: The young birds are beginning to show their colours. Photo by Colin Nakahara.

The adult bird is aware of Colin when he is on the roof and keeps an eye on him but has not been threatening or agitated. I hope to post more photos to show the growth of these beautiful birds!

Sunday Showcase: Birds of Late Spring

Here are some photos taken by Tony LePrieur in the Calgary region in mid-June. Many young birds have now fledged. The photos were taken in Fish Creek Park and at Frank lake.


American Avocet.


American Avocets with chick.


American Avocet.


American Avocet chick.


Great Horned Owl (juvenile).


White-faced Ibis.


Swainson’s Hawk with Meadow Vole.


Eastern Kingbird.


Western Kingbird.


Clay-colored Sparrow.


House Wren.


Least Flycatcher.


Cedar Waxwing.


Warbling Vireo.


American Coot with chick.

Do you have bird photos you’d like to share? Send them to our email address and we may post them.

Sunday Showcase: June Birds

Tony LePrieur got a nice variety of June birds last weekend in the Calgary area. Photos taken June 4-5, 2016 in Bridlewood, the Weaselhead, and at Frank Lake.


Wilson’s Phalaropes (foreground-female; background-male).


Pied-billed Grebe.


Yellow-headed Blackbird (male).


Cliff Swallows, collecting mud to build their nests.


American Robin (bebee).


Black-necked Stilts.


Yellow Warbler (male).


Swainson’s Hawk.


Wilson’s Snipe.


Yellow-bellied Sapsucker (female).

Sparrows, waterfowl, and warblers at South Glenmore Park

Posted by Dan Arndt

Our outing on May 3 took us to South Glenmore Park. Following our second week at Carburn Park, I headed over to the Glenmore Reservoir to try to find some water birds, and was able to get a couple photos of a distant female Red-breasted Merganser and White-winged Scoter, spurring on the visits for the following week. While we didn’t get either of them on our official outing, we did get a whole bunch of other great spring migrants, and had an amazing time finding all the new birds.

Red-breasted Merganser Pentax K-5 + Sigma 150-500@500mm 1/1250sec., ƒ/8.0, ISO 640

Red-breasted Merganser
Pentax K-5 + Sigma 150-500@500mm
1/1250sec., ƒ/8.0, ISO 640

White-winged Scoter Pentax K-5 + Sigma 150-500@500mm 1/1250sec., ƒ/8.0, ISO 640

White-winged Scoter
Pentax K-5 + Sigma 150-500@500mm
1/1250sec., ƒ/8.0, ISO 640

South Glenmore Park May 3, 2015

South Glenmore Park
May 3, 2015

For the past few years, a family of Common Ravens has nested right near the parking lot. Apparently this adult Raven has decided that peanut butter is a perfect breakfast treat. I like his thinking.

Common Raven Pentax K-5 + Sigma 150-500@500mm 1/800sec., ƒ/8.0, ISO 3200

Common Raven
Pentax K-5 + Sigma 150-500@500mm
1/800sec., ƒ/8.0, ISO 3200

As we walked around the point, we found Red-necked, Western, and Horned Grebes but sadly we couldn’t pick out a single Clark’s among over 75 Western Grebes. At least we had a couple Horned Grebes that were willing to let us get close.

Horned Grebe Pentax K-5 + Sigma 150-500@500mm 1/1000sec., ƒ/8.0, ISO 800

Horned Grebe
Pentax K-5 + Sigma 150-500@500mm
1/1000sec., ƒ/8.0, ISO 800

The view from the top of the hill above the main pathway allowed us to get even better looks at some of the Western Grebes out on the reservoir.

Western Grebes Pentax K-5 + Sigma 150-500@500mm 1/800sec., ƒ/8.0, ISO 400

Western Grebes
Pentax K-5 + Sigma 150-500@500mm
1/800sec., ƒ/8.0, ISO 400

In the trees along the ridge there were Tree Swallows and Northern Rough-winged Swallows hawking for insects above the canopy, but the most numerous songbird of the day was the Yellow-rumped Warbler. Along this stretch, there must have been at least 20 of them!

Yellow-rumped Warbler Pentax K-5 + Sigma 150-500@500mm 1/640sec., ƒ/8.0, ISO 800

Yellow-rumped Warbler
Pentax K-5 + Sigma 150-500@500mm
1/640sec., ƒ/8.0, ISO 800

Another new bird of the season was the Savannah Sparrow. This one seems to have a little less yellow in the lores than I’m used to, but his song was unmistakable!

Savannah Sparrow Pentax K-5 + Sigma 150-500@500mm 1/800sec., ƒ/8.0, ISO 800

Savannah Sparrow
Pentax K-5 + Sigma 150-500@500mm
1/800sec., ƒ/8.0, ISO 800

We then circled out to the west through the boreal and aspen parkland areas on the west end of the park, but came up with very little. We didn’t even see a single Common Loon on the entire reservoir that day, I think mostly because of how open the water was, and how many water bodies outside of the city were open after such a mild winter.

On our way back to the parking lot, we did have a close fly-by of this Swainson’s Hawk, one of our first ones of the season for the Sunday morning group!

Swainson's Hawk Pentax K-5 + Sigma 150-500@500mm 1/640sec., ƒ/7.1, ISO 500

Swainson’s Hawk
Pentax K-5 + Sigma 150-500@500mm
1/640sec., ƒ/7.1, ISO 500

As we returned to the parking lot, I decided that we hadn’t really had much luck with the sparrows on the pond, so sat in the grass and waited for them to pop out. I was welcomed very shortly after by both a White-crowned Sparrow as well as a Lincoln’s Sparrow. Well worth the effort!

Lincoln's Sparrow Pentax K-5 + Sigma 150-500@500mm 1/2000sec., ƒ/8.0, ISO 1600

Lincoln’s Sparrow
Pentax K-5 + Sigma 150-500@500mm
1/2000sec., ƒ/8.0, ISO 1600

White-crowned Sparrow Pentax K-5 + Sigma 150-500@500mm 1/1000sec., ƒ/8.0, ISO 1000

White-crowned Sparrow
Pentax K-5 + Sigma 150-500@500mm
1/1000sec., ƒ/8.0, ISO 1000

Have a great week, and good birding!

Wednesday Wings: Swainson’s Hawks

Posted by Bob Lefebvre

On Monday I was in north Glenmore Park, and there was a pair of Swainson’s Hawks there.  There was a stiff wind from the south, so I was able to get pictures as they soared almost motionless over my head.  One of the birds is an intermediate to dark adult, and the other is a light hawk that looks like it is just coming into its adult plumage.

There was a little corvid harrassment…

The two hawks together. 

Swainson’s Hawks

Swainson’s Hawks have started to arrive back in the Calgary region.  Now is a good time to reprint this article by Gus Yaki, which details the remarkable migration of these birds.  The article was written in February 2007 for the Bird Studies Group of Nature Calgary.  Reprinted by permission of Gus Yaki.

Meet the Species – Swainson’s Hawk

by Gustave J. Yaki

Right now (February 2007), almost all the Swainson’s Hawks of the world are in the Pampas, the treeless plains of South America, in central Argentina, Uruguay and Paraguay. The few exceptions are individuals trapped in the two appendages of North America.

One group of perhaps 50 birds, having made a mistake in navigation, or were blown off course, attempt to spend the winter in southern Florida, SW of Miami, between Homestead and the east boundary of Everglades National Park. Here they feed on insects and rodents in the temporary vegetable fields waiting to be turned into subdivisions.

Another group — several hundred birds, perhaps recent colonizers of southern California — have ended up in Baja California, Mexico. There, near Ciudad Constitucion, south of Loreto, an amazing diversity of cacti and other plant species, adapted to less than three inches of annual precipitation, have been bulldozed in order to grow wheat. Here, farmers are doing so by pumping up and spraying the fields with fossil water. The hawks feed on the grasshoppers and other arthropods living in those harvested grain fields.

Swainson’s Hawk.  Photo by Pat Bumstead.

But the really big story begins about now, at the southernmost end of the Swainson’s Hawks’ winter range, at latitude 34 degrees South, about on par with the city of Buenos Aires in Argentina.

I thought that we’d begin by following an adult female, equipped with a satellite radio transmitter placed on her by Stuart Houston of Saskatoon, in 1996, near Kindersley, SK, not far from the Alberta border. This transmitter was programmed to send a signal, one to four times in eight hours, every sixth day. (C.S. Houston, Blue Jay 57:2)

This female had already begun her migration on 13 Feb. 1997, when she was making a short reconnaissance around the area where she had spent most of the winter.

Six days later, by 19 Feb., she had moved a straight-line distance of 325 km northward. We don’t know if she traversed that distance all in one day or flew every day for an average of 54 km a day. Remember, she had been relatively sedentary most of the winter.

However, by 04 March, she was in Bolivia, an additional 1570 km. If she flew every day, she averaged 158 km a day for this  segment. By 10 March, she was in the upper Amazon area of Brazil, near Peru, a further distance of 1330 kms — or an average of 221 kms daily.

Obviously, she couldn’t have flown on days when it rained, as it often does there — at least not very far, so some days she must have covered greater distances. An adult female, trapped near Hanna, AB in 1995, over a 7-day period in Oct. and 2-three day periods in early November averaged 536, 565 and 473 km/day (J.K. Schmutz et al, Blue Jay 54:2).

Because the satellites take a north-south polar orbit, they are widely dispersed in the equatorial regions. The next signal was not received until nineteen days later, early on 29 March when she was in Chiapas in southern Mexico, a total accumulated, straight-line distance of 6,475 kms. She probably had crossed the Equator about the first day of our spring. She then traversed the Andes Mountains over Colombia to find the Isthmus of Panama. Once there, she mainly followed the Caribbean side of Panama and Costa Rica, before crossing to the Pacific side of Nicaragua, probably El Salvador, Guatemala and into Mexico.

Backing up a bit — by the time she reached northern Argentina, she would have been joined by thousands of other Swainson’s Hawks. In 1972, Neal Smith counted 344,409 Swainson’s passing over Ancon Hill, at the south end of the Panama Canal, near Panama City, during the autumn migration (J.K. Schmutz et al, Blue Jay 54:2).

Now, when migrating, the “Buteo” hawks seldom flap their wings, except to get air-borne. They make most of this long journey by using SOLAR energy.

When the sun shines, it heats the ground. This results in the air immediately above the soil being warmed, causing it to rise. Once the air temperature is above 10 degrees C, the rising air column is strong enough to lift the hawks high into the sky — like riding an elevator. Having gained the maximum lift on this “thermal”, as the rising air mass is called, our hawk set her course northward, and glided on to the next thermal, perhaps ten kms further along — to again be elevated, to repeat the process throughout the sunny part of the day.

Soaring Swainson’s.  Photo by Bob Lefebvre.

On clear days, at her starting point, latitude 34 South, she could have been aloft by 9 a.m. — and flown until 4 p.m. Nearer the equator, she could have been up much longer. I have seen hawks up, over Panama and Costa Rica in late March, flying as early as 7 a.m., and others still up at 5 p.m.

Once she had reached Panama, she was also flying with tens of thousands of Broad-winged Hawks and Turkey Vultures, as well as a few other species — a veritable river of raptors. By flying in a long column, the trailing hawks, watching the hawks ahead, are able to see where the next uplifting air mass is located.

As the day wears on and the sun begins to sinks in the west, the ground is no longer being adequately heated. The result is that the raptors lose their lift, and must descend to the earth for the night.

When 200,000 birds drop out of the sky into one area, there is no way that all can find food. So most hawks make the major part of this long journey on an empty stomach — as the lack of feces or whitewash below their nocturnal roost would suggest. However, uncomfortable as this may be, it can be advantageous. By not eating, birds are lighter, and therefore able to start flying earlier the next day — theoretically, getting to their destination sooner. They do, however, need to drink, to counter dehydration.

Having reached southern Chiapas in Mexico by 29 March, our female was next reported at Cotulla, just north of Laredo in south Texas on 04 April. Here, the hawks could spread out and feed again, if needed. No signal was received on 10 April, but by 16 April, she was at Lamar, Colorado. She was presumably still feeding and resting in this area, moving only another 170 km by 23 April. Perhaps there were no thermals or winds to assist her. Then a final jump of 1575 kms (a average of 263 km/day) brought her back to her previous year’s nest, where she was observed on 29 April.

She had completed a straight-line distance of 10,520 km in just under 11 weeks. Actually, her total journey would have been many thousands more kms if we could follow her compete path over the earth.

Not all the Swainson’s Hawks live in the nearby prairies. Some go on much further, to the Yukon and into the N.W. Territories to near the mouth of the Mackenzie River. Others go into eastern Alaska. Their migration is one of the longest in the bird world, certainly of the new world raptors.

Having reached her breeding area, presumably with her mate of previous years already there, being monogamous, she likely quickly re-mated, helped repair the old nest or build a new one, laid 2-4 speckled eggs, then began incubation — all within about two to three weeks. The earliest reported egg-laying date in Alberta is 06 May — the mean average date being 23 May (L. Priestly, Blue Jay, 63:1).  The eggs hatch 28 to 35 days later, usually between mid June and early July, with the mean date of 27 June.

The growing young, mainly fed young Richardson’s Ground Squirrels, remain in the nest — depending upon the weather and availability of food — for about another 45 days. They usually fledge in early August — the mean being 11 August — although young have still been in the nest as late as 03 Sep. The adults continue to feed the young for the next several weeks until they are able to successfully hunt for themselves.

In early September, Swainson’s Hawks begin to gather in small groups, in harvested grain fields. Here they now feed almost exclusively  on grasshoppers, averaging 100 of these a day. Accumulating in ever-growing numbers, they begin to slowly drift southward. By the end of September, virtually every healthy Swainson’s Hawk has left Canada, on average, a little over five months or 21 weeks after their spring arrival. In the case of Stuart Houston’s hawk, in 1996, she started her return journey, following a slightly different but parallel route, on 22 September and reached her wintering area by 30 November. There she spent the next eleven weeks — before starting the annual cycle all over again. Like other tropical migrants, she was experiencing Perpetual Summer.

Her spring migration equaled almost 11 weeks; the breeding season lasted almost 21 weeks; her autumn migration was 9 weeks; and her winter stopover was 11 weeks, for a total of 52 weeks. In total, she was in transit for 20 weeks, almost five months, just to have the opportunity to reproduce the next generation and perpetuate her species. — And just maybe, in the process — she filled those of us aware of her achievements, with awe and wonder!

Photo by Anne Elliott.

Longevity & other statistics

A Swainson’s Hawk banded as a nestling by   Edgar T. Jones of Edmonton, at Cereal, AB on 17 July 1988, was found dead at Quemu Quemu, LaPampa province, Argentina, in Feb. 2007. Having made 19 trips southbound and 18 northbound, Stuart Houston calculated that it would have travelled a minimum distance of over 400,000 kms during its migrations. (Blue Jay, 65:3, p.164)

Most Swainson’s Hawks do not nest until three years of age (B. Woodbridge et al, J. Raptor Res. 29), after having made three round trips.

A Swainson’s Hawk banded in California was still alive after 24 years (C.S. Houston, Blue Jay 63:1).

Swainson’s Hawk’s wingspread is 51 inches, compared to 49 inches for Red-tailed Hawks, which migrate only as far as Southern USA. The average Swainson’s weighs 855 g, compared to 1080 g for Red-tailed Hawks. (D.A. Sibley, 2000. The Sibley Guide to Birds, New York, Alfred A. Knopf).

In early 1996, Brian Woodbridge of California followed his radio-equipped hawks to Argentina. He thereby happened upon 700 dead hawks, killed by eating grasshoppers sprayed with the pesticide Monocrotophos, made by Ciba-Geigy. Two assistants, who visited sites of other radio-equipped birds also happened on massive kills. From 4847 carcasses examined, nine carried bands, seven of them from Alberta and Sask (C.S. Houston, 1996, Blue Jay 54(2). There was apparently a similar kill the year before, with at least one other banded bird from SK.