Utah Birds, Utah Birding, and Utah Birders. Promoting the sharing of information, and the conservation of habitat for birds in Utah and elsewhere. We are a group of people who want to share what we know, and create a positive birding experience in Utah.

BIRDERS BLOG

a blog by and for Utah Birders

Golden Eagle upperwings

posted by Jerry Liguori at
on Tuesday, May 31, 2011 


Now that Hawks at a Distance has been out for a few months, one comment I thought I would get but didn't yet, I'll address here. Yes, the Golden Eagle on the bottom right of page 155 (see photo above) has white on the upperside of the wings. Some people may think the white showing is the pale leading edge of the wings that many Golden Eagles show, appearing white due to the lighting. But, this individual actually has white on the upperwings. I published this ID pitfall before (pg. 125 of Hawks From Every Angle) and have seen it in the field many times. I even have a print of a Golden Eagle in my basement showing this very effect.

The fact is that some Golden Eagles, especially in the Intermountain West, actually have white areas on the upperwing coverts. People in Utah may know this from spending time in the West Desert where some of these birds with white on the upperwings occur. Maybe I should I have left that photo out of the guide, but too late now…and I wanted to show things that could be tricky in the field, and this is one of them!

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The Robin's Nest, My Head, and a Lesson Learned

posted by Jeff Bilsky at
on Monday, May 23, 2011 

Across the Street from my office is an open field lined by several tall trees that happen to attract a good number of passing birds. Last year I located a Northern Parula amongst other great birds and realized my own personal Patagonia Rest Stop Effect. I take as many meetings and phone calls as I can under those trees and often bring along the binos. I get weird looks from my co-workers but I don't care. I mean what do they do, sit at desks? Borrrrrring. So this afternoon I was checking the trees again and found several chattering Bullock's Orioles and singing Yellow Warblers. Then a Robin with a mouthful of worms landed on the nearby chain link fence. I observed it fly into an adjacent Pine and disappear. Intrigued I went in for a closer look. The Robin had mysteriously vanished. After probably close to 30 seconds I finally located the nest tucked into a clump of branches far off the main trunk. The Robin had apparently already left for the nest appeared unoccupied. I peered up just to take a look and catch a glimpse of nature. Nothing too invasive, certainly wouldn't dream of touching or reaching in, just wanting to revel in the beauty and appreciate this amazing and....wait what's this noise from behind me? Sounds like a Robin. Oh CRAP! A Robin with a mouthful of worms dove at my head like a patriot missile. I ducked just in the nick of time and immediately backed off several feet apologizing and insisting that all was fine and good and....."WHAT THE! WAIT!!!" Another dive right at my head and another narrow miss. I ran across the street like a mad man just in time to watch a co-worker giving me an odd look. The Robin went back to feeding her nest and I'll be witnessing nature from a safer distance for a bit. Good Birding and remember to respect their space.

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The Widow at the Window

posted by Jeff Bilsky at
on Friday, May 20, 2011 

Around my company I'm known as: "Bilsky, the guy who's in to birds." This gets me everything from weird looks, stares (mostly when I pull out my binocs to look at the trees across the street), jokes, and random bird-related questions. Recently I was in Florida, visiting my company's home office near Tampa, and my reputation had most definitely preceded me. One employee sought me out to ask my advice on the following dilemma...

Night after night he is being tormented by the call of the Chuck-will's-widow. It's described as a "seemingly endless call" by most accounts and my co-worker was desperate for a solution. He was at the point of considering capital punishment for the crime of sleep deprivation but I urged him to try other options - pointing out that the law frowns upon such things even if his weary eyes didn't. I also pointed out that the bird was only doing what it's evolution demanded. He seemed open to finding a way to co-exist peacefully and I suggested scaring the bird away with the call of the greatest predator of the night, the Great Horned Owl. The experiment is underway and thus far seems to be having mixed results. He reports that after his initial night of playing the owl call for 20 minutes the Widow left and didn't come back for nearly a week. Then he played the owl call again and the bird left...but then came back the next night. I wouldn't normally condone the use of an ipod in such a manner but I was trying to come up with a quick solution to help prevent the death of a Nightjar at the hands of the sleep-deprived. Apparently this is a community of a dozen or so homes that lives on the edge of the woods so there is no shortage of wildlife. He said that the community has decided to put up some owl boxes around the area to help control the burgeoning rodent population as well as to hopefully scare away the Chuck-will's-widows; perhaps the Barred Owl is a lullaby compared to the Widow.

Anyone have any other ideas on what to do in this situation or any similar stories about losing sleep because of a noisy bird?

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New eBird Data Entry

posted by Tim Avery at
on Wednesday, May 18, 2011 

eBird is finally making some much needed UI improvements to their website. They announced this week the all new data entry section and provided a link for current users to beta test the new interface and platform. Let me start by saying well done for starting to make the improvements to what is an outdated website. To be honest it was a little outdated in terms of looks from the get-go.

Step 1: Where did you bird?

The new interface is sleek and loses some of the tacky design flaws of the first version. It allows you to enter comments and age and sex information right on the checklist--a nice new feature that used to be after you had entered all your species. The right navigation that follows the user as they scroll has become very popular on a lot of websites,and it works well here, so that's a plus. It keeps important information visible as you scroll so you don't have to go back to the top.

Step 2: Date and Effort

It's not perfect however. I question some of the design--being a designer that's what I do. I don't love the single column checklist for starters. I'm not saying I like the current mess either. But somewhere in between, with a 2 or 3 column layout would shorten the page by 1/2 to 2/3 and make better use of the space available.

Step 3: What did you see or hear?

Now I spoke of the positive of the right nav, however it seems out of place on the right side. Fundamentally it makes sense to be on the left as the information there is stuff you would want to enter before you start adding your sightings. Not a major issue but something that as a UX designer bothers me.

Step 3: What did you see or hear?
(add details view)

And what about adding those details. I have to admit, I don't love the execution. It's in the right direction but could still use some work. The actual interaction and layout could be improved quite easily.

Your checklist has been submitted!

Overall, eBird is moving towards true north now. With some work and maybe hiring a UX consultant (right here--Chris and Brian I'm talking to you) there are some improvements that could be made to make the program even better. Maybe my next post will be a redesign of eBird I worked on a while ago for a side project. Anyways, thumbs up eBird--everyone else, you can check out the new data entry site below:

http://demo.ebird.org/ebird/submit

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Tom Parsons

posted by Jerry Liguori at
 


Tom Parsons, a friend and birding fixture at Cape May, NJ passed away this week. Everyone who knew Tom will recall him as the ultimate note taker, list keeper, and journal logger. He walked “the Point” every day jotting down every bird he saw. In fall, he would sit at the hawk watch every day after his morning walk and chat about birds and life. I truly enjoyed his company! He was an astute observer and a bit skeptical of my identifications, but grew to trust me, eventually telling me that he “had learned a great deal from me”. Coming from a man who had been birding his whole life, this was a great compliment. Tom loved to play devil’s advocate, but with a sensibility and respect so that any possible confrontation would never turn sour.

Tom was always a careful observer when it came to rare birds, taking detailed notes and precisely describing the particular patch a bird inhabited. He never drove or got a driver’s liscense…and only a few times did I see him hitch a ride to go see a rare bird. Tom mentions the 3,200 Great Blue herons I counted one day as his most memorable flight of birds ever at Cape May! For me, that is thrilling since Tom has seen thousands of impressive daily flights of birds.

He and his wife Peg had me over for dinner after each hawk watch season, and it was nice to get to know Tom away from birding where he was very open and comfortable in his own home. He spoke about teaching Zoology at the University of Toronto, and of being a fellow grad student with E.O Wilson. He also mentioned that his freshman advisor was Ludlow Griscom. Tom will be missed by all his friends and future birders at Cape May.

Photo above: Fred Mears (left), Tom Parsons (middle), and Bill Glaser (right)

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Issues with Blogger

posted by Tim Avery at
on Tuesday, May 17, 2011 

Last week Blogger had some database issues and in a 24 hour period lost all posts and comments that were created. This was about the time Ryan O'Donnell posted about Evening Grosbeaks and Carl Ingwell about Rainy Day Birding. Both posts disappeared for a while but came back. However, comments on both those posts as well as Jerry Liguori's post on Krider's were ALL lost and have not reappeared. If you posted comments and would like to post them again, please feel free to.

Sorry for any inconvenience that this may have caused, unfortunately we can't control much in terms of what happened in this instance as it was an issue outside our control.

Thanks for your continued support!

The Utah Birders

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Marathon Birding - A Mini Big Day

posted by Tim Avery at
on Monday, May 16, 2011 

Mark Stackhouse has run the Marathon Birding trip for a number of years at the Great Salt Lake Bird Festival and it was always a popular trip. About 5 years ago they decided to offer two versions with me leading another to accommodate the growing number of people interested in the trip. Last year Mark was unable to make it and the festival asked Jeff Bilsky to take on the trip. We decided to team up and lead the two 5 person trips together for a 10 person northern 2/3 Big Day—or Marathon Birding. It just so happened that the 10 person trip ended up outdoing all my previous trips for the total number of species in the day, with 141 tallied by end of day. So this year we decided to team up again and see what would happen again.

Nine people arrived by 6:00am at the festival headquarters in Farmington, along with 2 drivers, 12 Subway sandwiches, 2 cases of water, a host of binoculars, scopes, cameras, bird books and high hopes. After getting everything packed in the cars, signing our lives away, and quick introductions—we kicked off the birding on time with an AMERICAN ROBIN being the first bird of the trip, followed by BROWN-HEADED COWBIRD (both audible), and a fly over group of AMERICAN WHITE PELICANS. Lastly, before we piled into the vehicles Jeff pointed out an OSPREY perched in a dead Cottonwood several hundred yards away—the only Osprey we had for the day!

We drove into Farmington adding a couple “fly-bys” and “run-fasts” before making our first official stop at the ponds at the end of Glover Lane. We added nearly 40 species including a CACKLING GOOSE that has been around for a couple months, a drake BLUE-WINGED TEAL—the only of the day, and a number of other marsh birds. Moving onto Farmington Bay we found the gates closed—keeping us at the entrance to scan the first ponds, adding a few shorebirds, and the only RUDDY DUCK of the day. By 6:50am we were on the freeway headed to Antelope Island, with 50 species already on our list.

Western Tanager, the 2011 Spotlight Species

Driving from Layton to the causeway we added AMERICAN CROW for the group, and the lead car picked up a WESTERN TANAGER speeding across the road in front of us. I heard this was only the 2nd seen up to that point at the festival; a sour note since it was the spotlight bird this year. Once on the causeway we started adding new birds left and right—literally. First, on the left were about 10 LONG-BILLED CURLEW, then on the right 5 WHIMRBEL, a great find for the bird festival and in such numbers for Utah. Next we started seeing BLACK-BELLIED PLOVER—around 600 in total by the time we left. After a little scanning of the flats we turned up about 40 SNOWY PLOVERS around a ½ mile south of the road. Continuing across towards the island, we added both WILSON’S and RED-NECKED PHALAROPE as small flocks flew by and over the causeway in the strong winds.

Once on the island we grabbed CHUKAR, BEWICK’S and ROCK WREN, BREWER’S, LARK, CHIPPING, WHITE-CROWNED, and VESPER SPARROW, LOGGERHEAD SHRIKE, HORNED LARK, BURROWING, GREAT HORNED, and BARN OWL, and finally SAY’S PHOEBE. The only bird we missed that was expected was a Sage Thrasher. On schedule we took off heading for Willard Bay State Park. When we arrived the wind was in full effect as it was throughout the day. We added most of our expected species, with the exception of Gray Catbird and Eastern Kingbird. We missed a handful of more common species and the warbler diversity was slim. We did have 4 WESTERN TANAGER and the best bird of the morning in 4 EVENING GROSBEAK. A single LESSER GOLDFINCH and a beautiful COMMON LOON rounded out the surprises.

Common Loon at Willard Bay State Park

About 45 minutes behind schedule we headed north a little ways to Bear River MBR and drove a couple miles towards the refuge before turning back. We were hoping to turn up a Cattle Egret which we missed along I-15, but no such luck. Hoping to keep somewhat on schedule we headed east through Brigham City, adding RED-BREASTED MERGANSER at Mayor’s Pond before heading up Sardine Canyon and into Cache Valley. We drove up the west side through Mendon crossing the Bear River at Cutler Marsh where we got lucky with an AMERICAN BITTERN about 10 feet off the road. A great bird for the trip that everyone got to see.

American Bittern in Cache Valley

About an hour behind schedule we headed into Logan Canyon where the wind was whipping through the trees. Our normal picnic stop for lunch was closed, so we stopped at the next available location. As we unpacked to eat lunch there was a chattering whistle from the river. We walked in the direction of the sound, finding an AMERICAN DIPPER feeding another dipper. I expected it to be a mated pair but was shocked to find the bird being fed was a juvenile! Even more shocking was when I took my binoculars down and looked about 6 feet in front of us, spotting another young dipper flipping up twigs and leaves on the shore just in front of us! Everyone got great looks and some photos before we left the family to feed and feed ourselves.

American Dipper in Logan Canyon

After a little longer lunch than past years, we packed back up and headed higher into the mountains. We made one stop where we got looks as WHITE-THROATED SWIFT, VIOLET-GREEN SWALLOW, and SHARP-SHINNED HAWK. Continuing upward to where snow pack was still on both sides of the road, we stopped at Franklin Basin Road, just below Beaver Mountain where the surprise was nearly 50 “PINK-SIDED” DARK-EYED JUNCO. Usually we see a few Gray-headed, but the Pink-sided were a nice surprise. RED-NAPED SAPSUCKER, NORTHERN FLICKER, TOWNSEND’S SOLITAIRE, and HOUSE WREN were welcome additions before we made our way up to Beaver Mountain Ski Resort where the wind was howling and the birds were quiet.

A lone RUBY-CROWNED KINGLET sang away from one stand of conifer, while a flyover group of CASSIN’S FINCHES were heard by a couple of us. As we climbed the road towards the resort, I spotted what appeared to be a Goshawk. I got out yelling back and Jeff got out thinking he saw the same thing. The bird disappeared out of my sight and Jeff hollered it was a false alarm and just a Red-tailed Hawk. We got back in the car and continued up the hill when not even 100 yards up the distinct shrieking of a NORTHERN GOSHAWK came out of the trees by the road. We again hopped out as I yelled back to the second car about the bird, just in time to see an adult Goshawk soar out of trees chasing and then dive bombing a Red-tailed Hawk. As the birds passes I snagged my camera and managed two distant backlit shots before the hawk disappeared back into the forest.

Northern Goshawk in Logan Canyon

Unfortunately not everyone was able to see the bird as the quick event took place and was over in a matter of seconds. For those who did it was certainly a highlight for the day. After calming back down and finding no more birds at the resort, we headed east, picking up MOUNTAIN BLUEBIRD before dropping out of the mountains and down to Bear Lake. After refueling and almost 2 hours behind schedule we made our way to Sage Creek Junction to head south to Deseret Ranch. At the junction there was a ton of water in what is normally a dry ravine. A single CANVASBACK accompanied 3 REDHEAD, and a few NORTHERN PINTAIL. The Canvasback was our only of the day.

As we headed south now we stopped in Randolph spotting a COMMON GRACKLE perched in a tree in the middle of town. Jeff’s car spotted another as we passed through Woodruff. Hitting dirt road we made our way across Deseret Ranch, adding AMERICAN WIGEON and SAVANNAH SPARROW. The birding was rather slow and a few species were missed. But before we headed over the last hill a GOLDEN EAGLE soared over the road right over the first van, diving on a FERRUGINOUS HAWK, our only of the day and a good way to exit ranch.

Taking a quick dip over the border into Wyoming we visited Woodruff Narrows Reservoir where we tallied 50 species in about 30 minutes, the highlights being our first SAGE THRASHER of the day and a first for our marathon trips—a SAGE SPARROW that most of the group got to see running around with it’s tail straight up in the air. There were more shorebirds than I have ever seen in Wyoming on the south end of the reservoir, most were too far out to ID, but there were quite a few LONG-BILLED DOWITCHERS and both WILSON’S and RED-NECKED PHALAROPE. There were a few birds that I suspected were RED KNOTS, but they were too far out to be sure—and there were a couple hundred birds that were likely peeps, but at well over a mile away it was hard to tell.

With daylight running out, we hit the road, going through Evanston, and back in to Utah for about 70 miles of driving before we finally stopped again at Summit Park to try one last time for some coniferous species. MOUNTAIN CHICKADEE, STELLER’S JAY, and HAIRY WOODPECKER were all added to the list for the day, and a couple GREEN-TAILED TOWHEE gave everyone nice looks. As if the surprises throughout the day weren’t enough we added 3 BUSHTIT that seemingly came out of nowhere and were gone again after only a minute. As 8:00pm rolled around we made our way to Mountain Dell Reservoir, picking up SPOTTED TOWHEE a strange miss throughout the day until that point. With the last half hour of daylight we headed into Salt Lake City, making a pit stop before heading up Millcreek Canyon to go owling.

Unfortunately the wind never stopped once we made it to Desolation Trailhead. We hiked up the trail a ways and got away from the actual wind, but the entire 30 minutes we were there it was on and off in the trees above. This made it hard to hear anything. About half the group heard one or two toots from a FLAMMULATED OWL in between wind bursts, but with the conditions it just wasn’t a good night to keep looking.

And just like that the Marathon Birding trip was over. 132 species, 11,000 individual birds, 350 miles, and whole group of very tired, wind burnt birders called it a day. Looking back it’s astonishing what birds we missed; what birds we saw; and the strange things that seem to happen on days like this.

Take for instance the misses. How about Downy Woodpecker or Cedar Waxwing? Fox Sparrow or Red-breasted Nuthatch? Western Scrub Jay or Hermit Thrush? Those are all species we usually see. What about warblers? We tallied a grand total of 2 species on the day! That seems impossible on the ides of May—during the height of warbler migration; but it’s true. No Yellowthroat, Orange-crowned, MacGillivray’s, Black-throated Gray, or Virginia’s. We managed to miss Ring-necked Duck, and couldn’t turn up any lingering winter waterfowl. No Cattle Egret of Night-Heron. I could go on for a little longer, as there are about 25 species that would seem easy to find in May in northern Utah—but on a “big day” nothing is guaranteed and the Marathon Birding trip proved that year in and out.

The trade offs are the unexpected. The Grosbeaks, the Bittern, the Goshawk, the Bushtits—all make for great memories on these long days. They stand out as the “best birds”. But more interesting are the strange things like the Dipper with two fledglings at 7000’ in mid May. Thinking about it that means that bird was nesting as early as late March when 10’ of snow covered the banks of the river, and the icy water was carving its way down canyon. Seeing the young birds so close and the story that surrounds them getting to this point is more interesting than the rare birds for many people.

Another year and another bird festival in the books; and another Marathon Birding trip in the books. Now back to migration and hopefully some great summer weather!

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Ear Birding by Context.

posted by CarlIngwell at
 

A co-worker of mine and I were recently having a conversation about using context clues, and habitat, to help ID a bird by song. If you can narrow a song down to a few species based on the habitat you're in, the ID won't be so difficult. Easy concept, right?

This morning I was walking along, in a Pinon/Juniper hillside in western Colorado, when I heard a Vireo song. I was able to narrow it down to Plumbeous/Gray, and I decided that the notes were too fast and clear to be a Plumbeous; a Gray Vireo. No biggie, it was about the 10th Gray Vireo I had heard.

I looked up ahead of me and saw the bird singing, and it appeared very large for a Gray Vireo. I trained my binoculars on the bird, and I had a first year Cassin's Finch. At first I didn't think that the bird I was looking at was the bird singing. I kept my eye on the finch, and everytime the "Gray Vireo" would sing, the Cassin's Finch had it's bill open, pointed skyward, full of song.

I don't know much about Cassin's Finch as they're learning how to sing. Maybe they often sound like Gray Vireo, and I've just never noticed it because I've never heard that type of song come from a Cassin's in a Pinon/Juniper Habitat. Or, maybe Cassin's Finches, like some other finches, practice mimicry sometimes; if so, there were plenty of Gray Vireos they could pick up the song from.

Has anyone else heard a similar song from a Cassin's Finch, or has anyone ever heard them mimic another species?

Good day today. I also had a Northern Saw-Whet Owl calling on a point!

Love and cherish birds and all things.

Carl

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Evening Grosbeak Call Types

posted by Ryan O'Donnell at
on Wednesday, May 11, 2011 



Like Red Crossbills and Pine Grosbeaks, Evening Grosbeaks (Coccothraustes vespertinus) have been described as having distinct call types that vary geographically (Sewall et al. 2004). These distinct call types also correspond approximately with subspecies that have been described based on morphology. Because of these distinct call types which correlate to geography and morphology, it has been suggested that Evening Grosbeaks may be in need of further taxonomic work, that is, that they may be candidates for future splitting. In that Sewall et al. paper, they leave northern Utah as a question mark in their map, an unsampled area between the ranges of (morphologically-defined) subspecies C. v. brooksi and C. v. warreni, where no birds were examined and no calls recorded.

Yesterday I recorded a small flock of 4-6 Evening Grosbeaks calling in the treetops above my yard in Logan, Utah. Evening Grosbeak call types are distinct enough that they can be told apart by ear, but I don't have any practice at this so I imported recordings into the software RavenLite to examine the sonograms.

Most of the calls were of Type 1. This is the call type that is given by C. v. brooksi, the subspecies which ranges from Oregon, Idaho, and Wyoming north to northern British Columbia. Here is a sonogram of a Type 1 call I recorded yesterday:

And here is a recording of Type 1 calls from Washington you can listen to:


In my recording yesterday, I was also able to pick out a few examples of Type 4 calls in my recordings, which is typical of C. v. warreni and mapped by Sewell et al. as occurring from about the Uintah Mountains, through Colorado, to northern Arizona and northern New Mexico. Here is a sonogram of one of the Type 4 calls from my yard:


And here are some Type 4 calls from Colorado you can listen to:


Sewall et al. documented both call types 1 and 4 from northwestern Wyoming and southern Colorado. It appears that both call types also occur in northern Utah. More work will have to be done to tell whether this is the result of movement of individuals, intergradation between subspecies, or overlap between reproductively isolated cryptic species.

Sewall, K., R. Kelsey, and T. P. Hahn. 2004. Discrete variants of Evening Grosbeak flight calls. Condor 106:161-165.

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Rainy Day Post

posted by CarlIngwell at
 

Last night I camped in a beautiful location near Naturita, Colorado. A Common Poorwill was singing me to sleep.

This morning's transect was pretty nice before the rain came. I had a handful of Sage Sparrows, Vesper Sparrows, Brewer's Sparrows, Chipping Sparrows, Lark Sparrows, Spotted Towhees, Ash-throated Flycatchers, Gray Flycatchers, and Say's Phoebes.

The rain started to come down pretty hard around the middle of my transect, so I headed back, hoping to avoid slippery roads. The traction wasn't too bad on my 7 mile drive out, and the rental Kia handled pretty well. It's continued to rain since I left, and I'm assuming the roads are impassable now.

Rainy, rainy, rainy. The Naturita library doesn't open until 10:00, so I'm wasting time, bumming internet off the visitor center (which is also closed; I'm sitting in the parking lot on my laptop).

I guess this is more of a listserv post, but oh well. Life is grand and I enjoy being a field tech.

Carl

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Krider's!!!

posted by Jerry Liguori at
on Tuesday, May 10, 2011 

A recent post on the Idaho listserv of a Ferruginous Hawk made me think to write this entry. A quiz photo of a juvenile light-morph Ferruginous Hawk was posted and the possibility of it being a Krider's Red-tailed Hawk was discussed. A common ID problem....I think I even show the two side-by-side in "Hawks From Every Angle".

I won't go into detail on how to separate the 2 (I posted a short response on the site), I just wanted to post 3 Krider's Red-tailed Hawks here showing how pale and lightly marked underneath they can be (adults on left and center, juvenile molting on right. Bird on right by Brian Sullivan.

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Birders are silly.

posted by CarlIngwell at
on Monday, May 9, 2011 

It's funny how birders will drive 6 hours to see a rare bird in St. George, but that same rare bird could be located 6 hours away over a state line & few would care :).

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Consider me a traitor.

posted by CarlIngwell at
on Sunday, May 8, 2011 

Well, the field season has started, and I'll be doing surveys in western Colorado this year. I can promise you all entertaining stories from up and down the Western Slope, but I can't promise you any good Utah bird sightings this summer :(.

I hope that is okay with everyone, and I hope you all don't vote to kick me off the blog as I'll no longer primarily be a "Utah Birder." I promise to write a lot in the field, and I'll share with you whenever I'm home.

So far I've found that Colorado has just as many lions, rattlesnakes, coyotes and scorpions. They have more Sage Sparrows and Palm Warblers & less Snowy Plovers and Arches. Should be a fun season.

Carl

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Nocturnal Migration Part 3 - Base Reflectivity

posted by Tim Avery at
on Wednesday, May 4, 2011 

Base Reflectivity basically corresponds to the amount of radiation that is scattered or reflected back to the radar by whatever targets are located in the radar beam at a given location. These targets can be hydrometeors (snow, rain drops, hail, cloud drops or ice particles) or other targets (dust, smoke, birds, airplanes, insects).

The colors on the Base Reflectivity product correspond to the intensity of the radiation that was received by the radar antenna from a given location.

So how does this translate into numbers that make sense?

Other targets and hydrometeors show up in the same spectrum of reflectivity as one another. However, one key difference is the intensity at which they show up. To the left you can see the full spectrum of dBZ from -30 to 80.

Next to that are numbers for hydrometeors which show the actual millimeters per hour of precipitation in relation to the reflectivity.

To the right of that are the estimated number of birds per kilometer cubed. As you can see the non precipitation reflectivity is much lower on the scale and only go up to about 35 dBZ. Occasionally it does go higher, but that is rare.

In both scales, the higher the dBZ the higher the corresponding numbers are. So the more intense the weather, the more water that falls. The more intense the migration reflectivity, the higher the number of individual birds migrating.

In the radar images above, you can see the dBZ differences between the birds on the left, and the weather on the right. The radar image on the left is an example of a very nice night of migration around 25 dBZ in the center (the green area). This was taken on May 3 at around 10pm mountain time over the Oklahoma/Nebraska state line.

In my next post I will talk about why the radar image appears in a Donut shape, and about the velocity of the migrants.

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