Showing posts with label birds. Show all posts
Showing posts with label birds. Show all posts

Sunday, January 19, 2014

Steller Jay Communication and Research

You may have seen me lurking in your neighbors yard or driving up and down Hwy 20 in a Jeep with Montana plates. I'm not lost. I am a visiting PhD student from the University of Montana and I am here to study the Steller's jays of the Methow Valley

My research is focused on how animals communicate about danger and predators and a part of this is trying to figure out how Steller's jays combine two alarm calls and mimicry to encode information about predators.

I use a variety of playbacks to elicit different calls and behaviors at different bird feeders throughout the valley. The research is going well, although because of the mild winter the birds are less dependent on feeders and therefore a little more difficult to work with. However, the people, views and copious amounts of bakeries have eased that frustration. If you see me out and about, feel free to stop me and ask questions and I hope to see most of you at the talk summing up my research here on January 23rd.

Thanks for all of your help and support! 

Community Soup and Presentation:  
January 23, 2014.  Steller's Jay Communication by Alexis Billings, University of Montana PhD student - presentation at the North Cascades Basecamp in Mazama. 5:30pm soup dinner, 6:00pm presentation.  8$/person (bring a friend- $10 for 2). 

Tuesday, September 17, 2013

Raptor Migration

The Fourth Annual Raptor Migration Festival fulfilled expectations this year with great raptor viewing from Chelan Ridge to Harts Pass.  The North Cascades Basecamp was proud to be involved with a booth at Pateros Memorial Park. A crowd of 30 joined us at the Basecamp on Saturday night for summer garden vegetable curry soup and emmer brownies with ice cream dessert, followed by a great presentation by Andy Stepniewski of Yakima Audubon.   

Andy and Ellen led 15+ participants up to Harts Pass on Sunday morning to watch more of the migration magic.  The sunny ridgeline was ideal on this day for migrating raptors; wings set back, head thrust forward, and hardly a flap needed except for the balancing act to overcompensate for gusts of wind reaching 20-30 mph.  The highlight of the day was acrobatic prairie falcons at the Slate Peak parking area, numerous osprey riding the winds, and rocket-fast merlins chasing pipets.  We watched over 50 birds in their migration south, catching those thermals and riding the gusty winds.  Happy travels and we’ll see you next year! 

Wednesday, June 19, 2013

Co-evolution of the red-naped and red-breasted sapsuckers

The red-breasted Sphyrapicus ruber and red-naped Sphyrapicus nuchalis sapsuckers are two woodpecker species that overlap in their range near the crest of the Cascades.  These two species are sympatric, meaning that during the evolution process, they became two new species while inhabiting the same geographic region. Generally speaking in Washington, the red-breasted live on the west side, the red-naped on the east side.   At the North Cascades Basecamp in Mazama, we’ve had the opportunity to observe both species in a cedar and birch grove that is unique to the upper Methow watershed.

This year, a male red-breasted sapsucker was observed late in the winter along the Basecamp trail.  He drummed his broken drum on local snags, showed off his beautiful red head, called his quiet “mewing” call, and even excavated a perfectly round cavity in a birch snag.  A female red-naped sapsucker was often seen in the same area, licking (not drinking) up sap with her barbed tongue, making frequent visits to his territory, and exploring the newly constructed cavity with intrepidation (poking her head up to the entrance but not entering).  Finally in mid-June, after many hours of observation, we saw the red-breasted male and the red-naped female both enter and exist the nesting cavity with food in beak for the hungry nestlings, and he was being a good dad and dropping fecal sacs to the ground as his housecleaning duties ensued.   

These two species of sapsuckers are known to hybridize in south-central Oregon, northeastern California, along the California-Nevada border, and in southern Nevada.  Genetic studies by Johnson et al (1983, 1985) showed that red-naped and red-breasted sapsuckers have the highest avian genetic relatedness ever reported, similar to that found between avian subspecies.  They also found the hybrid F1 generation to produce viable offspring, although it seems that certain F2 backcrossings may have partial sterility issues.  These studies and others confirm that although these two species are nearly genetically identical, there is a low degree of hybridization while encountering each other regularly, and therefore they are still considered as separate biological species. 

It will be interesting to see what our new fledgling hybrid sapsuckers look like, and who they choose as mates into the future.

Ned K. Johnson and Robert M. Zink. 1983. Speciation in Sapsuckers (Sphyrapicus): I. Genetic Differentiation.  The Auk: 871-884.

Ned K. Johnson and Carla Bowman Johnson.  1985.  Speciation in Sapsuckers (Sphyrapicus): II. Sympatry, Hybridization, and Mate Preference in S. ruber daggetti and S. nuchalis.  The Auk: 1-15.

Thursday, May 16, 2013

Birding extravaganza at the Basecamp - May 16th!

A birding morning by the birch forest today was amazing- especially the red-breasted sapsucker!  And here is proof- we believe it is a male, who is coming and going from a newly excavated cavity in a birch snag.  Even more exciting is the female red-napped sapsucker in the area, who is visiting the cavity and poking her head inside while the red-breasted is inside... but not entering. 

Here are the birds Steve and I encountered this morning:  7:30-9:00am, partially sunny, cooler temps than last week, and the height of breeding song here in Mazama. 

Townsend's warblers
Wilson's warblers
Yellow-rumped warblers
Nashville warblers
Pacific wren (AKA winter wren)
House wren
Cassin's vireo
Warbling vireo
Varied thrush
Hammond's flycatcher
Black-chinned hummingbird
Caliope's hummingbird
Red-napped sapsucker
Red-breasted sapsucker
Golden-crowned kinglets
American robin
American crow

Wednesday, February 20, 2013

Bald Eagle Surveys- Winter Foraging

Last Sunday, January 27th, the North Cascades Basecamp lead another successful wintering bald eagle survey in the valley. After spotting our first eagle, a 1st year juvenile, within minutes of meeting at the Barn in Winthrop, we took off. This winter, there seems to be fewer eagles in the Winthrop to Mazama area than last year. This is likely due to a small to minimal run of steelhead migrating back to the hatchery this winter, which differs from last January/February.  It also could be the result of a minimal deer mortality, since the deer have easy access to food this year; With hard winter years, there are more deer mortalities and therefore increased food resources for these scavengers. Another theory is that deeper snow in the Winthrop area during the winter pushes the eagles down-valley, looking for more food and foraging opportunities.    Regardless, we took off south to find eagles.
A 2-year juvenile perched shows off its beautiful mottling. 
We began to spot bald eagles along the East Country Road near Twisp where the cows are calving, leaving the fields littered with placentas, a nutritious meal for a bald eagle.  There was also an unidentified carcass (most likely a deer) in the field, which also attracted attention from eagles, ravens, and crows. In total, we saw 17 bald eagles at this site. Several were perched in cottonwoods around the field’s perimeter, while others feasted on the carcass. There was a nice array of juveniles at the field. The group got great views of 1st, 2nd, and 3rd year olds, allowing us to see the progression in plumage, beak, and eye color.
An adult bald eagle watches over a carcass.
If you look close you can see the
blood on it's face! 
As we continued south along East 20 and 153, we saw 7 more eagles perched in trees near the river. We finally pulled over and discovered one of the night roosts the eagles are using this winter. From 4:45PM – 5:10PM we saw 22 birds fly in to the area to spend the night. We saw 12 of these eagles (6 adults and 6 juveniles) fly to into a portion of the night roost right off the road. As they perched, they noisily communicated with each other. We also saw 8 eagles head up a valley about 200 meters further south. These eagles were most likely headed to a different night roost, although we lost sight of them behind a hill, and do not know where exactly they ended up. We are excited to find out in upcoming surveys!

Want to join us next time? We are heading out again on February 10th and 24th,1-5:30pm; cost is $20/person.  Email, or call (509)996-2334 for more information.

Thursday, January 24, 2013

Wintering Bald Eagle Surveys in the Methow Valley

This winter, naturalists are braving the cold temperatures while joining the North Cascades Basecamp to survey bald eagle distribution and night roosting locations in the mid to upper Methow Valley.  On January 13th,  five intrepid explorers documented 11 eagles between Twisp and Carlton, three of which were spotted as they were flying into their evening roost. One highlight included an up-close view of several perched juveniles eagles, likely feasting on prey near the river below, as their beaks were covered with blood. 

One-year bald eagle juvenile near Carlton. 
Notice the blood on its beak!

As the group is observing and documenting bald eagles and their locations, they are also becoming skilled at aging these slow to mature birds. Observers expected one of the eagles to be a first-year bird (born in 2012) as it’s head was dark brown, beak had very little yellow on it, and its eyes were still dark brown.  At two years of age, bald eagles have more yellow developing on their beak, lighter brown eyes, a lighter golden brown head, some white mottling on their chest, and a fair amount of white on the underside of their wings. At three years, they have further lightened heads, beak, and eyes, as well as a dark brown stripe behind their eyes. A four-year juvenile resembles a mature adult, except for some minimal brown speckling on their head and tail.   Other highlights of the surveys include great views of an adult golden eagle, two red tail hawks, and two rough-legged hawks near Twisp. 
Three-year old bald eagle juvenile with white 
on top of head and dark stripe behind the eye. 
If you’d like to learn more about bald eagles and join these surveys with the North Cascades Basecamp, surveys are every other Sunday between 1-5:30pm; cost is $20/person.  Email, or call (509)996-2334 for more information.

Saturday, January 19, 2013

Winter Wildlife Tracking

On Saturday morning, a determined group of eight gathered near the cozy fire in the North Cascades Basecamp Lodge. We listened as our animal tracking guide, Gabe Spence, described his experience learning about tracks, following animals footprints in all environments, and how we would do just that here in the Methow. 
The group examines our
first track sighting

As we embarked into the snowy landscape in Mazama, the conditions proved perfect for tracking. The sun was shining, the snow was soft, the temperature cold enough (as in 3 degrees...brrr!) to have preserved every movement of the animals over the last 3 days.
Gabe identifying tracks

With Gabe’s help, the group quickly spotted tracks with two large imprints in front and two smaller and offset imprints behind. The medium sized animal must hop given the distance between the tracks, and since frogs are out of the season, we decided on the snowshoe hare. 

Snow shoe hare track
These quick and industrious hares seem to do well in this environment  as we saw their tracks on many occasions.  The  low hanging trees provide fir needles, buds and twig snacks for their seasonal diet. Deer, whose tracks we also found close by in the forest, also devour similar woody treats during the winter season. 

Not only were we able to identify animal tracks, but many of the prints in the snow told the story behind the animal’s movement. Our investigations found motivation behind an animal’s directional movements and the speed of their gait. As one member of the group said, “we are like detectives, using clues to tell us what happened!”
The group following coyote tracks near Beaver Pond

Before returning for lunch, we followed tracks we initially believed to be one coyote. Our group carefully walked alongside the prints and eventually recognized that three coyotes were tracking lunch of their own 

The coyotes’ footprints led us to a tree where we found another animal’s tracks and remains of their lunch: pine cone remnants. Clearly, the coyotes were hoping to feast on unsuspecting red squirrels. The coyotes’ movements through the trees harboring squirrels explained their thinking and know-how to find their prey. 

After warming our cold toes by the fire and a hearty lunch at the Basecamp, we drove to another site in Mazama where Gabe frequently spots cougars. Though we did not find cougar evidence on this day, we found many tracks that would likely be a cougar feast. Deer, weasel, field mice, and coyote tracks lay preserved for examination. 
Small tracks hurried for
shelter in the snow

We finished our tracking day by following a deer. Deer tracks are usually clearly identifiable but can be tricky depending on the snow conditions. Their long, thin legs and heavy bodies leave connected strides forming a squared off trough in the deep snow where many deer have walked.  

In the deep now, deer, much like snow shoers, will generally follow one another, staying in the tracks already laid by another thus saving time and energy.  In the deep powder snow, it was difficult to determine the direction of travel since last week’s snow most often fell into the tracks, obscuring the actual footprint.  After much discussion, we learned from Gabe that in these conditions, the leading pointed edge of the hoof where the track is deeper indicates the direction the deer traveled.

The group after a fun day following tracks!
It was with trepidation that many members of the group took off gloves to put their hand into the snow of the deep track. They found out which direction the deer was walking, exposing their fingers to the frigid temperatures. We continued following the tracks which eventually led us to our parked cars. The deer must have known we were all chilly after an exciting day in the great outdoors. 

Wednesday, September 19, 2012

Raptor migration festival weekend

a snowy owl and golden eagle in Pateros
The Third Annual Raptor Migration Festival was a great time this year with many participants enjoying the weekend.  The weather held out for a weekend of great raptor viewing at Chelan Ridge and Harts Pass.  The North Cascades Basecamp was proud to be involved with face painting at Pateros Memorial Park. 

A crowd joined us at the Basecamp on Saturday night for summer squash soup and homemade bread, live raptors from WSU Raptor Rehab Center, and a great presentation by Jim Watson (WDFW Raptor Research Biologist) about his collective 40 years of studying raptor migrations.  Jim led another 15 participants up to Harts Pass on Sunday morning to watch more of the migration magic.  The highlight of the day was continual great views of 2 juvenile prairie falcons unsuccessfully hunting a hoary marmot (quite a sight indeed) and resting on rock and tree perches at the Slate Peak parking area.  We watched over 40 birds in their migration south, catching those thermals and riding the gusty winds.  Happy travels and we’ll see you next year! 

Harts Pass field trip
Raptors observed at Harts Pass on Sunday, September 9th, 2012
sharp shinned hawk- 12
red tailed hawk-15
golden eagle-1
prairie falcon- 2 juv, 1 ad fem
unidentified falcon- 2
merlin- 3
osprey- 1
American kestral- 2
harrier hawk- 1
coopers hawk- 1

Friday, July 27, 2012

Calliope's Hummingbird Chicks Have Fledged!

July 19th- The chicks are eighteen days old today and after having been gone for two days I was excited to see the presence of flight feathers. Over their head and back they are that brown w/red tipped color, but also have a greenish tinge now. The feathers on their wings are longer and black, there are also solid white feathers toward the back of their wings and tail. Their little beaks are mostly black now with some yellow at the base. Their chins are solid white in color.

July 20th-  I checked on the chicks right before a thunderstorm hit Mazama and the Basecamp. The chicks were sitting close together. There was generally no change in their appearance between day 18 and 19.

July 21st- The chicks are twenty days old today, the number of days predicted for a Calliope's hummingbird to fledge.. which sure enough was right on! I checked on them this morning to find that they had survived the wind and rain of the storm in the protected foliage of the forest. Both chicks woke up when I arrived, they also appeared to be much greener in color. I took a few pictures, and as I turned to leaved both chicks flew out of the nest. I was able to turn around and see one of them fly up into a neighboring tree!

Monday, July 16, 2012

Hummingbird Update!

 Remember these tiny little Calliope's hummingbird hatchlings? 

Thursday July 12th, 2012
Today the first hatched chick is twelve days old, and the second chick is eleven days old. The chicks are much larger, and definitely fill up the whole nest. Their feathers are short, even in length and distribution. The feathers are dark brown with white tips. Their orange beaks have elongated but are not as long as a mature hummingbird's. They were nestled in the nest facing the same direction, and breathing very fast but probably normal for a hummingbird.

Sunday July 15th, 2012
Today the chicks are fifteen and fourteen days old. The weather is dynamic today, with some thunder, wind, and sun. Amazingly, the big leaf maple branch that is carrying the hummingbird nest is very reliable, the chicks do not seemed phased. The chicks eyes were open for the first time in my observations which was awesome to see, they are looking around and blinking a lot, also drifting in and out of sleep. Their beaks have definitely developed into longer (approx. 1.5 cm), thinner, and stronger beaks. The beak coloring is now red/orange at the base with yellow edges; the tip is black.

As far as feather coloring and texture goes, the chicks have short, white, feathers on their chins and also slightly above the beak. From the top of their head and covering their back the feathers are a mixture of some solid white feathers and some brown feathers with reddish tips. These feathers are short and smooth and even in length. They are less evenly distributed than the previous observation. They also still have light brown downy feathers that stick up along their backs. These chicks should fledge in about five days!

Wednesday, July 4, 2012

Calliope Hummingbirds- Daily observations on a mother and her chicks!

On Friday June 29th at eleven a.m. Amelia, Emmet, Kim, Mica and I walked down the trail to the river a short ways to a hummingbird nest that Amelia had found earlier in the day. Carefully assembled on a thin, drooping, leafy branch about six feet above the ground was the tiny nest. It was a small and cup shaped, about five inches in length. Hummingbird nests are made by the female from materials like cotton from cottonwood trees strewn together by spiderwebs which is really cool. On top of the nest the female arranges lichen, possibly for camouflage. When we came to the nest the mom hummingbird was sitting on it. As we took a step closer she flew away with the typical whirring noise that hummingbirds make. Now we were able to look inside the nest to find that there were two, tiny, white, elliptical shaped eggs! Hummingbirds lay about two eggs 1-3 days apart. Amelia had seen only one egg the day before so the second one must have been laid today.

Two days later on Sunday July 1st one of the chicks hatched! This time Amelia, Emmet and I took a ladder to the area and waited until the mom flew away so we could easily peek into the nest. Amelia was the first to see the baby hummingbird and was so excited. Sure enough, when Emmet and I looked we found a little purplish colored chick with a few crumpled feathers sticking out.

The next afternoon on Monday July 2nd, Kim and I took our cameras down to photograph the chick but the mom stayed on the nest the whole time so we tried not to disturb her and left. Around seven p.m. Amelia and I tried to see the chicks one more time and this time the mom wasn't on the nest! We set up our ladder to look into the nest and found two chicks. The babies had their eyes closed and still only a few feathers. I took a picture of them and the broken egg shells left over in the nest. Later that night we brought Steve and Emmet down to see the chicks too.

On Tuesday July 3rd, day three for the first hatchling and day two for the second, the mom was sitting on the nest when I arrived to see them. She flew away though and I was able to see the chicks. Today both of them were moving their bodies and heads while opening their short orange beaks too! Their eyes also appeared larger and rounder today. I left shortly after looking at them so the mom could come back as soon as possible.

Facts about Calliope Hummingbirds:

  • Scientific Name: Stellula calliope. The Calliope Hummingbird is distinct enough to have its own genera.
  • Habitat: Coniferous mountains, meadows, forested hillsides
  • Breeding Season: Mid-May to August, they are single-brooded.
  • Eggs: Usually 2 elliptical or sub elliptical, white, 12x8 mm eggs.
  • Incubation: Only the female incubates and later cares for her offspring. Incubation usually lasts 15-18 days. 
  • Nestling: Altricial
  • Nestling period: Brooded and fed regurgitated nectar for 11-12 days. Fed arthropods delivered by the female until they reach 21-23 days when they will become fledglings. 
  • Conservation: Little is known about many hummingbird populations because they are difficult to study. The only species thought to be in decline may be the Rufous Hummingbird due to some habitat loss. Habitat loss in Mexico and Central America is a potential threat to hummingbirds. 
  • Hummingbird Fun Fact: A hummingbirds heart rate is 1250 beats per minute while in flight!
Works Cited:
Sibley, David. The Sibley Guide to Birds. New York: Alfred A. Knopf, 2000. Print.

Thursday, June 7, 2012

Spring Festival: Celebrating Birds and Botany in the Methow Valley

Last weekend  was the 2nd Annual Spring Festival where we welcomed the birds back to the Methow Valley and danced amongst the flowers of spring in Mazama.  The weekend was full of field trips with birders and botanists alike.  This included an early morning bird walk starting at 6am with Steve Bondi, birding by ear with Libby Shriner and Victor Glick, birding and botanizing with Dana Visalli and Joe Arnett, wildflower walk with Eric Burr, and a riparian bird walk with Howard Ferguson and Scott Fitkin.  Presentations focused on the interactions between plants and birds and their co-evolution together over the millenia.

Saturday's festival activities included the Native Plant Society's booth naming all the crazy human-made, natural, and weed plant items that make up birds' nests as we picked our way through 10 nests from different species.  The most unique items were the snakeskin and spider webs, straw wrappers, bailing twine, and plastics woven into the nests. The owl pellet station kept kids and adults busy, identifying and gluing small mammal parts onto a black piece of paper for a final take home project.  Bruce helped us make basketry woven nests from serviceberry boughs, wool, dried grass, bark and leaves.  The Audubon Society station had life-sized and hand-painted birds positioned in their respective habitats, with field guides and binoculars for easy identification.  And lastly, the Community School Kids invited everyone to be a bird and migrate south in a game that helped learn the hazards and benefits of long-distance migrations.  Lastly, Okanogan Wildlife League Lisa Lyndsay stood with live raptors on-hand, showing off Pigwigeon the screech owl, a sweet-tempered great horned owl, a stubborn red-tailed hawk, and dizzy the kestral.

The day of activities was topped off by Sam Lucy and Linda Robertson's poetry reading at noon, where everyone was taken back by their grace and inspiring words of spring!

Sunday, January 8, 2012

Wintering Bald Eagles in the Methow Valley

On Saturday, Jan 7th Libby and I led a field trip observing and discussing wintering bald eagles throughout the Methow Valley.  The highlight was the 15 eagles we saw at the confluence of the Methow River and Spring Creek, just in Winthrop.  We had many opportunities to age many juveniles, from 1 year olds with dark feathers and dark eyes, to approximately 4 year olds with mottled bodies, wings and head.  We were able to see Coho salmon, and mallards and common mergansers in the shallows of the river,  all favorite food of the eagles this time of the year. We also headed to the Big Valley area, where road kill deer had been freshly scavenged on by coyotes, eagles, ravens, and magpies.
After lunch at the Rocking Horse Bakery in Winthrop, we ended our day with a night roost survey south of Carlton.  Unfortunately, an individual was target practicing with their shotgun at the roosting location, and their shots flushed the eagles off the roost and they left the area.  Amelia and I had counted at least 15 eagles at the roost location the evening before.  The group had a great time, even with the cold temperatures of the day.  We ended up counting at least 25 eagles in the mid-Valley area.

Monday, October 24, 2011

Habitat for the Birds

At the North Cascades Basecamp in Mazama, songbird habitat along the Audubon Certified trails to the Methow River is native and wild and the upper bench surrounding the lodge and cabin feel naturalized and cared for.  However we realize the parking areas and the grass/tree component of the facility was missing some critical habitat for birds, SHRUBS!   So, we gathered root balls of native plants from our own property, used our kids and wheelbarrows to haul plants up the hill, and marked out the areas of interest.   

With the help of Pacific Crest Outward Bound students this October, they volunteered 50 person hours to turn a gravel parking area into a bird sanctuary for years to come.  Together we made this happen by ridding the parking lot of gravel, tilling the site and digging holes in hard-panned earth, laying down compost, creating a walking path, and planting and mulching native shrubs throughout the area.  We are extremely pleased on how quickly a parking lot has transformed into a new native shrub area to welcome the birds back in the spring! 

Plants we collected and used for our restoration site include:  
* spirea * mountain ash * serviceberry * oregon grape * kinickinick * boxwood * ocean spray * chokecherry * hawthorne * woods rose * sitka rose * red-osier dogwood

Sunday, August 21, 2011

New Chicks

 We have a new set of chicks here at the Basecamp this summer, and we've been having fun watching them grow.  They are now 6 weeks old, and integrating well into the flock of 1 1/2 yr old hens we already have.  We had a beautiful Barred Rock rooster (hence the 6 black&white chicks) who graciously gave DNA to all our hens, however none of them wanted to sit on eggs.  So without a hen willing to do the job, we borrowed "Broody Mama" from our friends the Bard family in Twisp.  She willingly took our dozen fertilized eggs, sat on them for the exact 21 days, and successfully hatched eight chicks.  As a mother, she takes her job very seriously protecting her chicks and letting them forage first on the array of leftovers from Basecamp guests and the family garden harvest.  Hopefully we'll get hens out of the batch of chicks;  too young to know yet.  All eggs from our girls go into our meals here at the Basecamp, and we love that orange color and bold flavor you don't get from store-bought eggs.

Saturday, August 20, 2011

Brown-headed Cowbirds

We had an interesting encounter this spring in our own backyard here at the North Cascades Basecamp with something we talk and teach about on a regular basis...  nest parasitism.  We found a ground nest of juncos with an intruder amongst them; a brow-headed cowbird chick (chick on the top-left in the photo).  Notice the new feathers already coming in on the cowbird chick, however the juncos hardly have their down.  It is also significantly larger than the other babies.

Mama and Papa junco diligently were caring for their own trio of juncos, but this babe (the cowbird, chick #4) kept growing and eating, and eventually the juncos were looking a bit lethargic due to their unwanted sibling's ability to grow faster, eat more, and even squish them out of the nest.  Here is more information about the species from the Smithsonian Migratory Bird Center.

What is a Cowbird?

The brown-headed cowbird (Molothrus ater) is a brood parasite that lays its eggs in the nests of other birds. These "foster parents", called hosts, usually raise cowbird young at the expense of their own eggs or young.
Cowbirds earned their common name from the habit of following herds of buffalo (and cattle) in search of the insect prey that were flushed up by the large grazing mammals.

Portrait of a Parasite

Cowbirds have been called songbird chickens because they can lay more eggs than any other wild bird. A single female is capable of laying nearly one egg per day at the peak of the breeding season, and produces a total of 30-40 eggs over the 2-3 month breeding period (May-July). Because female cowbirds usually lay only one egg in a host nest, this translates into 30-40 nests parasitized (usually of at least several different species) per female in one season.

Typically, female cowbirds find potential host nests by perching during early morning hours in a location with high visibility such as a dead tree in a forest opening, observing behavior of host females that are building nests, and following the unsuspecting birds directly to their nests. Once the nest location is known, the cowbird returns during the egg-laying period of the host female and deposits her own egg in the nest. By parasitizing during the host egg-laying period, the female cowbird improves her chances that the host female will be away from the nest often (allowing the cowbird access without being detected), and that the cowbird egg will be accepted by the host and receive full incubation.

In approximately 60-70% of nests parasitized, the cowbird removes one of the host eggs before laying her own egg. This is possibly to ensure that the host does not "notice" a different number of eggs in the nest, or to ensure that the cowbird egg receives full incubation (an extra egg laid in the nest could make it difficult for the female to incubate all eggs evenly, resulting in some eggs—possibly the cowbird's—failing to hatch).  Cowbird eggs require an incubation period of only 11-12 days, whereas most host species require 12-14 days, and some as many as 17 days of incubation. Consequently, cowbird young hatch earlier than the host young, affording the parasite a distinct advantage in competing for food with its younger foster siblings.

Cowbirds tend to parasitize birds smaller in size than themselves. For example, by the time they are ready to leave (fledge) the nest, most warbler or vireo (the most common cowbird hosts) nestlings weigh less than half as much as cowbird nestlings. In fact, a fledgling cowbird is larger than the adult warblers and vireos! The monstrous cowbird nestling not only can cause host young to starve by monopolizing the food supply brought by parent birds but also literally may crowd host young right out of the nest.

All of these attributes of the parasite can add up to severe effects on the host family. Impacts of parasitism are different for different host species, but usually result in loss of at least one, and often all, of the 3-5 host young. Although each cowbird female only lays one egg in a nest, a high abundance of cowbirds in an area often will lead to many cowbirds parasitizing the same limited supply of host nests. The presence of more than one cowbird in a nest almost inevitably leads to death of all host young. In addition, raising even one cowbird can potentially reduce the survival of host parents because of the increased physical effort needed to care for the ravenous intruder.