This was a GREAT DAY!  We could have only exceeded ourselves in a very few ways.  While we saw just about everything our hearts could desire, we did not, as far as I know, see any intermediate or dark morph buteos (Red-tail, Ferruginous, or Rough-leg), and no owls.  Also, we saw no Lapland Longspurs, though they were likely in the vicinity, and we saw no white geese.

What we did see was eight raptor species.  That’s darn good!  First of all, we saw several Northern Harriers.  These guys are not very common in the summer, but they are fairly common on the eastern plains in the winter.  They are strikingly sexually dimorphic with a slender body and long wings and tail.  The very handsome smaller male is light gray above with a mostly white breast and belly with strong black tipping to the flight feathers (primaries dipped in ink).  The much larger female is brown above and is buffy with brown streaks below.  The distinctive juvenile bears a superficial resemblance to the female but is darker brown above and rufous below.  They all have an obvious white rump patch, and when viewed from head-on its fairly easy to see their owl-like facial disc which performs a similar function as with owls enhancing hearing and prey detection.  They are typically seen gliding on dihedral wings and lazily flapping low over fields and marshes (prior to 1982 they were called Marsh Hawk).  An interesting aside, juveniles have dark eyes while the adults have yellow eyes; it’s just opposite to the buteos.

The majority of our Bald Eagles were adults with maybe only 4-5 of them being sub-adults – it takes these guys five years to obtain full adult plumage.  It makes me wonder if the lack of juveniles is an indicator of how tough it is to live long enough to become an adult.  While Red-tailed Hawks can be extremely variable (about 15% are dark morph individuals), it appeared that most, if not all, of our birds were light-morph western Red-tails (westerns have a dark chin and easterns have a white chin, among other things).  As for the Ferruginous Hawks, which are our largest buteos, they are extremely uncommon in the summer, but are a common winter resident on the eastern plains.  We struck out seeing any dark morphs, which make up about 10% of the population, but we got good looks at a number of light-morph juveniles and adults.  

Rough-legged Hawks are a true panboreal arctic species breeding in the northern taiga and arctic tundra.  They can begin to show up on their wintering grounds in Colorado in November, but peak numbers are generally not reached until late December or early January, and by mid-February numbers are already declining as birds begin to move back north.  While it’s possible to differentiate the male, female, and juvenile there is an extreme amount of variation in the plumage of the light-morph individuals which make up 90% of the population.  This is a long-winged species distinguished by its small bill and feet and its capacity for hovering while hunting.  Getting to see these beautiful hawks is always a treat!

Perhaps the big find of the day is that we saw three falcon species, and possibly a fourth.  American Kestrels are a fairly common year-round resident, so we can tend to count on them.  The other three species are a less certain deal.  Merlins nest in southwestern and central Wyoming, and there are two confirmed historical breeding records for Colorado from 1877 and 1887.  Additionally, there have been a few summer sightings.  However, The Second Colorado Breeding Bird Atlas (2016) says zilch about Merlins, either currently or historically.  So, for now, we view Merlins strictly as a rare to uncommon migrant and winter resident.  One thing to be aware of is that there are nine subspecies of Merlin, 6 in Eurasia and 3 in North America.  All three of our North American subspecies have been recorded in Colorado, but by far the most common is the Prairie Merlin which is distinctly paler than the other two subspecies.  The male has a pale bluish-gray cap and back and a black tail with 3-4 broad pale bluish-gray bands; the female has a pale brown cap and back and a black tail with 3-4 broad pale brown bands.  They both have a thin white supercilium and white underparts lightly streaked with brown.

Prairie Falcons are rare summer residents on the eastern plains, becoming slightly more common in the winter.  This can be especially true when Horned Larks are present in large numbers, which appears to be the case this year.  Peregrine Falcons are very rare in the winter in Colorado, and though possible (and I have had two winter sightings) it just doesn’t occur very often.  We may have had one on Saturday, but I didn’t get to see it myself.

Okay!  Enough for now.  We will be visiting the eastern plains looking for raptors again on Feb 25.

Chuck

Southeast of Barr Lake (88^th to 128^th) Jan 28, 2023

20 Species

9 Participants

1500 Cackling/Canada Goose
140 Rock Pigeon (Feral Pigeon) 
4 Eurasian Collared-Dove
1 Mourning Dove
10 Northern Harrier
19 Bald Eagle
7 Red-tailed Hawk
5 Rough-legged Hawk
11 Ferruginous Hawk
3 American Kestrel
3 Merlin (Prairie) 
1 Prairie Falcon
4 Black-billed Magpie
1 Common Raven
1092 Horned Lark
200 European Starling
3 American Robin
15 House Sparrow
19 Western Meadowlark
800 Red-winged Blackbird