About us: We own the Wild Birds Unlimited nature shop in East Lansing, Michigan,
a store that provides a wide variety of supplies to help you enjoy the birdwatching hobby.

This blog was created to answer frequently asked questions & to share nature stories and photographs.
To contribute, email me at bloubird@gmail.com.

Tuesday, March 31, 2015

Eagle Optics Wild Turkey Binocular introduces New BIRP Technology

The future of birding has arrived! Featuring revolutionary technology, the Wild Turkey takes a shot at what was previously thought impossible. We're sure you'll want to gobble it up!

The new BIRP Technology - Bird Image Recognition and Playback allows you to plug your headphones into your binocular to identify what you are focused on in the field. https://youtu.be/a53w35--K8k

Early birds also get the best mates

The morning air is alive with birdsong in the spring. Birds can sing at any time of day, but during the dawn chorus their songs are often louder, livelier, and more frequent. It’s made up mostly of male birds, attempting to attract mates and warn other males away from their territories. There are a few theories on why birds think dawn is the best time to sing a solo.

One idea is that in the early morning, light levels are too dim for birds to do much foraging but it’s a great opportunity to sing. Another idea is that early morning singing signals to other birds about the strength and vitality of the singer. Singing loud and proud first thing in the morning tells everyone within hearing distance that you were strong and healthy enough to survive the night. This is attractive to potential mates, and lets your competitors know you’re still around and in charge of your territory. Also dawn songs are clearer and more consistent, which allows individual males’ signature songs to be identified easily by their bird neighbors.

Later in the spring, when males sing while the female songbirds lay their eggs in early morning it may reinforce the bond with the female, and dissuade other males from jumping into the nest.

And if you think the birds seem to be singing even earlier in the morning than last year, you could be correct. Research by biologist Mark W. Miller found that in 1929 the first robin songs began about 45 minutes before sunrise, but 84 years later with our neighborhoods flooded in artificial light, robins tended to break their silence more than an hour earlier.
 
References:
- Brown, T. J. and Handford, P. (2003). Why birds sing at dawn: the role of consistent song transmission. Ibis 145: 120-129. doi: 10.1046/j.1474-919X.2003.00130.x.
- Hutchinson, J. M. C. (2002). Two explanations of the dawn chorus compared: how monotonically changing light levels favour a short break from singing. Animal Behaviour 64: 527-539. doi: 10.1006/anbe.2002.3091.
- Outdoors: Predawn bird songs fading soon by Mark Blazis http://ning.it/LT6Xvk
- American robin song by Patterson Clark http://goo.gl/ERk2f

Monday, March 30, 2015

Why I have mud in the bird bath

I'll admit it. Sometimes my bird bath gets dirty but when I saw a BIG MUD clump in the bath yesterday it took me a couple seconds to put the pieces together. American Robin nesting season has begun!

The American Robins choose their Michigan nesting territories in March and they are excited to start nesting. That means they need a lot of grasses and mud to build the perfect nest.

Unfortunately my excited female couldn't find any unfrozen mud to begin construction. She brought a bunch of frozen grasses and dirt to the bath in hopes of getting a jump-start in creating nest building materials. I'm not sure how much mud she took away but she left a lot behind.

Females build the nest from the inside out, pressing dead grass and twigs into a cup shape using the wrist of one wing. Other materials include paper, feathers, rootlets, or moss in addition to grass and twigs. Once the cup is formed, she reinforces the nest using soft mud gathered from worm castings to make a heavy, sturdy nest. She then lines the nest with fine dry grass. The finished nest is 6-8 inches across and 3-6 inches high.
 
Related Articles:
- Why Robins are Attracted to Water http://bit.ly/qP9aTs
- Bird of the Week: American Robin http://bit.ly/pnUKqk
- Fun Facts About The American Robin http://bit.ly/n9CSni
- Why robins are called Robin Redbreast and not orange breast http://goo.gl/OB4iT
Sources:  
AllAboutBirds http://www.allaboutbirds.org/guide/American_Robin/lifehistory 
Robin building a nest video https://youtu.be/fqgPmnW8yCU?t=2m11s

Sunday, March 29, 2015

When orioles migrate north to Michigan

When do the orioles arrive?

October through February most orioles hang out in American tropics and Southern Mexico southward. March and April some orioles begin moving north. On average, they probably travel about 150 miles each night in flocks, flying at about 20 miles per hour. If the weather is favorable, it will take an oriole about 2-3 weeks to complete his migration north to reach my mid-Michigan window again by May.

I always say orioles are the last to arrive in the spring and first to leave in the summer. I'll have my feeder on the window at the East Lansing Wild Birds Unlimited store up by the end of April waiting for him arrive.

Orioles eat a variety of fruits, nectar, bugs, and nuts. The best way to attract orioles to your yard is with feeders that offer suet, nuts, mealworms, nectar, grape jelly, or fruit (oranges, grapes, apples).

In July orioles become more secretive. As Baltimore Oriole babies become independent, parents begin their fall molt and are more susceptible to predators as they grow a new set of feathers. Peak migration is August and September but some begin as early as July if they are done nesting.

Related Articles:
Can birds predict the weather? http://bit.ly/w3bhs8
Facts on the Baltimore Oriole http://bit.ly/GzSTbi
Where do orioles winter? http://bit.ly/GAeWv5
Close-up of Baltimore Oriole http://bit.ly/GAf6T7
Favorite Oriole feeders http://t.co/OjG4Lz4

Saturday, March 28, 2015

Summer birds arrive: Importance of feeding birds in spring

While I love my winter birds, I can’t wait for some of the spring and summer birds to arrive; Rose-breasted Grosbeaks, Indigo Buntings, wrens, hummingbirds, orioles, Song and Chipping Sparrows to name just a few. Soon the American Goldfinches will all be sunny yellow.

Spring is the hardest time for birds to find food as many prime food sources are depleted. Bird feeders provide an easy source for birds after a long winter or arduous migration. Many birds migrating to their nesting grounds may see yards with lots of bird activity as a safe stop-over point. The numbers and variety of birds appearing in your yard can actually change every morning as species such as warblers, vireos, tanagers, gnatcatchers, kinglets and sparrows all migrate north.

In the spring, birds have a long “to-do” list and a short time to accomplish it. They claim territory, seek out mates, build nests and begin to raise their young. With so many birds arriving there’s a lot of competition. Offering foods makes everything a little easier to accomplish.
 
Birds that have survived winter in good health are best suited for getting reproduction going as soon as possible. A wide variety of studies have shown that providing supplemental foods permits birds to begin reproduction earlier with better success. The additional food helps them have more eggs per nest, bigger eggs, better hatchability, faster nestling growth, and lower nestling mortality. Feeding is especially helpful in years when storms and other natural disasters happen.

Backyard bird watchers can enjoy a variety of birds up close and wait eagerly for the new babies to arrive at the feeders and baths. In the summer, even if there is a lot of food available for birds, believe me, energy requirements are high when you have many mouths to feed and sometimes they just appreciate a night out at the feeders. 

Related Articles:
What seed is best for attracting the colorful birds? http://goo.gl/SAA35
What are the differences between the Wild Birds Unlimited seed blends? http://goo.gl/lF0rr
What seeds do wild birds eat? http://goo.gl/MjUCA
When should I feed the birds? http://goo.gl/IvocS

Friday, March 27, 2015

Photo Share: Monarchs are migrating north

Monarchs on Verbena Bonariensis, Great Butterfly plant! - Holly
At last! The news we've all been waiting for came from Estela on March 24th:
"Hundreds of monarchs are flying over Angangueo —right now—with a clear direction northward! I am quite sure this is the mass leaving. It's a wonderful sunny day, and a gentle north wind is assisting the monarchs as they begin their long journey." -the Journey North
Monarch Butterfly Migration MapThe first Monarch you see in the spring may be the grandchild of the last Monarch you saw in the fall. Spring is a critical time for monarchs. Their numbers are at their lowest point at this time of year. The old generation is dying. A new generation must grow and survive. You can track their migration on the Monarch Butterfly Migration Map.

Related Articles:
- Do Monarch Butterflies just wake up in the spring? http://goo.gl/5tkUk
- Monarch migration route http://goo.gl/L66ty
- Punctuation Butterflies: The First Butterfly of Spring! http://bit.ly/JHUpG1  
- How Fast Does a Monarch Butterfly Fly? http://bit.ly/ywhpZr
- Did you know butterflies have ears on their wings? http://bit.ly/x04qEi
  
Thank you Holly for sharing your photos of monarchs! If anyone else would like to share a photograph of nature send it to bloubird@gmail.com and I'll put it on the Friday Photo posts. 

Thursday, March 26, 2015

Stop bird crashes into windows

Window alert decals prevent migrating birds from trying to fly through your windows.
Right now bird migration is underway throughout the area and unfortunately the change in light and the unfamiliar surroundings cause birds to fall victim to window strikes. Window strikes are hard to totally eliminate, but there are ways to reduce them and/or reduce their severity:
  • Decals like Window Alert placed on the outside of windows have had the most positive feedback from customers. Each decal contains a component which brilliantly reflects ultraviolet sunlight. This ultraviolet light is invisible to humans, but glows like a stoplight for birds.
  •  Locate feeders and birdbaths within 1-2 feet of them so they can't gather enough speed to cause significant injury or about 20-30 feet from windows so birds have time to change direction.
  • Window screens will reduce injury even if a bird flies into it. Use them where practical.
  • Mylar reflective strips hanging loose in front of the window will move in the breeze and alert birds flying too close to a window.
It is estimated that between 100 million and one billion birds are killed every year in the United States when they crash into glass windows. 

If you do have a window strike and the bird is injured CALL FOR ADVICE! 
The best course may be no interference. For a list of licensed rehabilitators in our area click HERE.
For a complete list of Michigan Licensed Rehabilitators visit the Michigan Department of Natural Resources at: http://www.michigandnr.com/dlr/
Or to search for a local wildlife rehabilitation group by zip code at: http://www.wildliferehabber.org/

Wednesday, March 25, 2015

Plants to attract butterflies

Young black swallowtail http://www.pbase.com/rcm1840/lifecycleofblsw
caterpillar on parsley (host plant)
Make sure you have plants to feed butterfly caterpillars to bring more butterflies in to your yard. In many cases, caterpillars of a species feed on only a very limited variety of plants and cause little leaf damage. 

The Plants Common Butterflies Caterpillars' Eat:
  • Monarch - milkweeds
  • Viceroy - willows, cottonwood, aspen
  • Black Swallowtail - parsley, dill, fennel, common rue
  • Eastern Tiger Swallowtail - wild black cherry, ash, tulip tree, willow
  • Giant Swallowtail - prickly ash, citrus, common rue, hoptree, gas plant, torchwood
  • Zebra Swallowtail - pawpaw
  • Painted Lady- thistles, mallows, nievitas, yellow fiddleneck
  • Red Admiral - wild cherries, black oaks, aspens, yellow and black birch
  • Coral Hairstreak - wild black cherry, American and chickasaw plum, black chokeberry
  • Dun Skipper - sedges, grasses including purpletop
  • Gray Comma - gooseberry, azalea, elm
  • Henry's Elfin - redbud, dahoon and yaupon hollies, maple-leaved viburnum, blueberries
  • Pygmy Blue - saltbush, lamb's quarters, pigweed
  • Silver-Spotted Skipper - locusts, wisteria, other legumes
  • Sulphurs - clover, peas, vetch, alfalfa, asters
  • Variegated Fritillary - passion flower, maypop, violets, stonecrop, purslane
  • Woodland Skipper - grasses
Download the Attracting Butterflies tip sheet (pdf) 
Source:  National Wildlife Federation
Photos Shared by Holly. Thank you Holly for sharing snapshots from your beautiful yard.

Tuesday, March 24, 2015

Cardinal mating call

In February Northern Cardinals formalize their choice of mate for the nesting season. The female chooses a male and they sing to each other. Both sexes sing clear, whistled songs, which are repeated several times, then varied.

Some common phrases are described as purdy, purdy, purdy…whoit, whoit, whoit, whoit and what-cheer, what-cheer…wheet, wheet, wheet, wheet.

By March territories have been decided and you will often see mated pairs at the feeders together. They like to eat next to each other and the male cardinal often shares his meal with the female in a mate-feeding behavior.

By April, if all goes as planned, they usually have started to raise their first of two broods.

Related Articles:
Northern Cardinal Fun Facts http://bit.ly/twE6NV
How the Northern Cardinal bird was named http://bit.ly/tSKZYs
Cardinal Bird Feeders Made in the USA: http://bit.ly/qXJPFM
How to Attract Cardinals: http://bit.ly/pjh7mO
What can I feed the cardinals to make them redder? http://bit.ly/rAArXw
What are the different types of cardinal birds? http://goo.gl/CUI43

Monday, March 23, 2015

Head banging birds

There are varied signs of spring: migrating birds passing through, new songs in the air, and the earth slowly waking up from its long winter nap. And there is another sign that is just as predictable which you’ve noticed, the bird battles.

The testosterone levels in male birds is up in the spring, territories are being determined, and battles break out. Two house sparrows in a seemingly endless wrestling match is not uncommon. It’s usually a bloodless battle that ends when they are distracted or one bird taps out.

Cardinals and Robins are also choosing their nesting territory. Their winged battles are usually short lived with a clear winner decided. The exception is when they spot a competitor that is about the same size and coloring. I’m already getting calls about cardinals and robins attacking their reflection in the window. This is also a territorial behavior.

They are usually unattached males without a female to direct them in a productive direction. Most birds do stop after a couple weeks of window pounding in the spring, but it's better to try and deter the birds just in case it turns out to be an action that is performed so often that it becomes almost an involuntary response.

Some tips to deter bird window attacks:

• Cover the window with screens
• Shut the blinds on your windows when you are not at home and at night.
• Rub the window with a bar of soap or squirt with liquid soap to decrease the reflection.
• Hang balloons or Flutter Scare tape.* Anything that moves and repels the bird from that area will be effective.
• Post a hawk silhouette outside a window.* Hawks prey on birds, so their images will keep birds from flying towards your window.
• Install a window feeder.* This breaks the reflection and other birds interrupt the birds battles with himself.

*Available at Wild Birds Unlimited - East Lansing, MI

Sunday, March 22, 2015

Attract goldfinches to your garden

When do the goldfinches return to Michigan?
Male and female American Goldfinches at Nyjer feeder in summer colors.
March is the goldfinches’ transition time. Just as the daffodils bloom, the male goldfinches exchange their dull winter coat for their bright yellow plumage.
You can see yellow feathers and a black cap coming.
.
Many customers think the American Goldfinches disappear in the winter. Actually, in the fall both male and female goldfinches molt into an olive brown plumage, but continue to feed actively in Michigan. In the spring the male turns bright yellow again with a black cap, wings, and tail, and white rump. The female keeps the duller brown color and lacks the black cap.
 .
Molting can take a lot of energy and feeders full high fat foods like Sunflower or Nyjer thistle are the easiest way to attract the American Goldfinches. Habitat is also important. In this case you do less work, not more. They love to eat dandelion and grass seeds and don't cut off the tops of your Marigold, Zinnias, Cosmos, or Coneflowers...Goldfinches love them. A row of sunflowers along the fence can attract finches as well as a variety of other birds too.
 .
And if you don’t have a natural water source nearby, set up a bird bath. Place it among shrubs and low-branched trees so goldfinches can keep watch for predators while descending gradually toward the water. Wild birds can obtain some water from their food, but goldfinches are vegetarians and like to sip from shallow baths where available to wet their whistle.

Related Articles:
European Goldfinches http://bit.ly/Q2Cu37
Goldfinch Migration http://bit.ly/MzGSPD
Are Goldfinches here in the winter? http://bit.ly/PZu5ML
Goldfinches: The Last Birds Nesting http://bit.ly/PZuejj
Bird of the week: American Goldfinch http://bit.ly/PZum2a

Saturday, March 21, 2015

Best way to mount Bluebird Boxes

Because bluebirds lack a strong bill to excavate a cavity for nesting, they depend on finding the used cavities of other birds or man-made houses. Bluebird populations had declined steadily over the years due to habitat loss. But, thanks to man-made houses, they are making a comeback. Our Wild Birds Unlimited bluebird boxes are designed with the birds in mind.

The top can be lifted for viewing without disturbing the nestling and easy monitoring of the nest-(it is not recommended to open the box day 13 or after as this may cause fledglings to leave the nest too early). The side is easily opened at the end of the nest season for cleaning. It is important to clean out old nesting material that may harbor parasites.

Mounting Bluebird Boxes 

Locate in an open, grassy field edge or lawn area away from trees (300 ft or more apart). Place the houses at least 50 feet away from birdfeeders and your main house. Face the box away from prevailing winds (facing south) and mount boxes approximately 5 feet high. Perching areas near to the nestbox like telephone poles, stakes, small trees, etc. are preferred by bluebirds.

If Tree Swallows compete for the nest site, place another box near the first (15 to 25 feet from the original house). They seem to tolerate overlapping territories of other species, but bluebirds will not nest less than 300 feet from each other. Both swallows and bluebirds are dependent on cavities for nesting, but otherwise they are different in many of their survival strategies. Bluebirds feed on ground-dwelling insects while swallows feed on insects in the air. Given places to nest, they can coexist within an area quite effectively. It may even be beneficial for bluebirds to have swallows nearby to warn them of potential predators or danger.

One important item to mention is that sparrows may try to take over a bluebird nesting box. They may find the box first or they may try to force the bluebirds out. The only way to help reduce this possibility is to make sure the house is mounted away from the edge of trees or away from human dwellings and to remove the nests before they are complete (a sparrow nest is a sloppy collection of grasses or litter that fills the box). You can also leave the top and side of the nestbox open to make it less desirable until the sparrow relinquishes its claim on that house.

Friday, March 20, 2015

Photo Share: Spring begins!

Female birds have a voice of their own

The drab female Northern Cardinal isn’t as flashy as her brilliant red male counterpart, but that doesn’t make her a push-over.

Females sing to call in male cardinals when they are eligible and want to be courted and during courtship they match their mate’s songs. Later female cardinals sing to shoo away brightly colored mates from the nest when a predator is nearby. Then they give the all clear, when it is safe or they want a meal delivered.
A female cardinal in her breeding plumage. - Rodney Campbell
Thank you for sharing! You can see more of Rodney Campbell’s work at: http://rodney-campbell.artistwebsites.com/art/all/birds/all If anyone else would like to share a photograph of nature send it to bloubird@gmail.com and I'll put it on the Friday Photo posts.

Thursday, March 19, 2015

Protect the entrance to your bird house

Bird House Portal Protector

Have your squirrels decided to expand the hole size on your bird house and move in themselves? Metal portal protectors prevent unwanted birds or other animals from enlarging the entrance holes on your bird houses. Or they can be placed over an already expanded hole to correct the opening size.

There are three sizes available at the Wild Birds Unlimited East Lansing, MI store. You can choose the 1½ inch opening to allow bluebirds, swallows, Carolina Wren or sparrows access or choose the 1¼ inchto allow access to only the smaller birds like titmice or chickadees. And the 1 1/8 inch portal protector only allows in the tiny House Wrens.

The metal portal protector rings have 2 holes pre-drilled and 2 screws included for easy attachment. It does not deter birds from entering.

Related Articles:
5 Tips to Attract Birds to Nest in your Bird Houses http://bit.ly/xETceZ
Common Bird House Problems http://bit.ly/wrWzyN
Which Way Do You Face a Birdhouse? http://bit.ly/AD43TW
Don’t use treated lumber to build a birdhouse http://bit.ly/x2pIG0
When do birds begin nesting? http://bit.ly/wbJ3kE
DO NOT Collect Dryer Lint for the birds to use as nesting material! http://bit.ly/wC5HcO

Wednesday, March 18, 2015

Help migrating birds by creating stopover sites

Rose-breasted Grosbeak start to appear at the end of April
As you might imagine, migration takes a toll on the birds. It is not uncommon for birds to lose one-fourth to one-half of their body weight as they migrate thousands of miles. Before the journey north to their breeding grounds birds accumulate fat to help maintain their energy reserves. Sometimes, however, reserves are not enough. That’s where you can help by creating “stopover sites” in your yard with plenty of food, water and shelter.

At this time of year the numbers and variety of birds appearing in your yard can actually change every morning as many small songbirds migrate through the night. Species such as warblers, vireos, orioles, grosbeaks, tanagers, buntings and sparrows all migrate overnight.

Some reasons are to avoid the heat of the day, windy conditions, and predators. Many species use the stars in the night sky to guide them, and there is some evidence that, perhaps, magnetic fields at the poles help guide them.

Other large-winged birds such as hawks, eagles, vultures and even pelicans migrate during the day, as they rely on thermals and updrafts to fuel their flight. They are efficient flyers and use very little energy during migration, allowing the wind to fuel their flight.

When you think about migration facts, it is astonishing to learn of the amazing feat that many birds accomplish twice each year as they move between their summer and winter range and back again.

Related Articles:
- The Journey North: Bird Migration Maps http://bit.ly/pbk4Eb
- Great Horned Owl Singing at Night http://bit.ly/qKeKDM
- Are Horned Larks Common in Mid-Michigan? http://bit.ly/qmAbt7
- How do Birds Migrate? http://bit.ly/nNCI6d
- What birds migrate from Michigan? http://bit.ly/qa0CVU

Tuesday, March 17, 2015

Red-winged blackbird singing is a harbinger of spring

This seemed like a long winter winter without respite. So yesterday when it got warm enough to open the door at the Wild Birds Unlimited store in East Lansing, I was so happy to hear the loud konk-a-ree, ogle-reeeeeee of the Red-winged Blackbird.

The redwings are among our earliest spring migrants. Mid-March is when the male Red-winged Blackbirds arrive in mid-Michigan. The females will arrive a little later.

The male Red-winged Blackbird Agelaius phoeniceus is an all black bird with red shoulder patches edged in yellow. The female and juvenile have heavily streaked underparts and mottled brown upperparts.

Some people don’t like to have the Red-winged blackbirds at their feeder in the spring because they are loud and messy and eat a lot. While there’s some truth to that, Red-winged blackbirds also consume large numbers insects and weed seeds, so they have their good points as well. And when the rains come in the spring, the bugs are sure to follow and then we’ll be happy they eat so much.

Red-wings return to breed at or near the same hatching or nesting site every year. Then once they are done nesting, they begin to wander and form large flocks in preparation for migration. In the wild, a Red-winged Blackbird's lifespan averages 2.14 years, but the oldest red-winged recorded was 15 years 9 months old.

Related Articles:
Red-winged Blackbird facts http://bit.ly/yQPs61
Blackbird Battle http://bit.ly/xFsHIN
Red-winged blackbirds attack hawk http://bit.ly/yaudwu
Singing Birds Herald The Arrival of Spring http://bit.ly/xibvfI
How to Prepare Your Yard for Spring http://bit.ly/zUs3EP

Monday, March 16, 2015

Wild bird nest material

I want to put nesting material out to help with the nest building. I'm thinking hair from hairbrushes, yarn, paper strips and maybe cotton. Does anyone know what the best thing to put out would be? What should I avoid putting out there for them? How early should I start doing so? – Thanks


Alpaca wool has microscopic air pockets that make it an excellent insulator.
It’s lightweight and durable and also repels water and dries quickly.
Supplies a soft, warm interior for bird nests –
and lets you watch nesting activities from your window.
Simply hang near your bird feeders or bird houses.
The birds that winter in our area, (chickadees, bluebirds, titmice, house finches, sparrows, and cardinals) may begin collecting nesting material as early as March.

It depends a lot on the weather. They are looking for potential nest sites now and as soon as the weather permits they will begin nest building. If bad weather rolls in they will suspend building until it rolls out again.

Birds that migrate further south for the winter, (wrens, hummingbirds, swallows, orioles, buntings, grosbeaks, and warblers) usually become situated in their summer territories and look for nesting material in May.

Some birds have only one family. Others can have two or three clutches and will look for more nesting material throughout the summer. And the American Goldfinches don’t even begin to nest until late summer. So it is good to have nesting material out from March until October to attract a wide variety of birds to nest in your area.

At Wild Birds Unlimited East Lansing, MI store we have cotton nesting balls, bison down bags, alpaca wool, and Birdie bells full of grasses, cotton, animal hair and feathers. Or you can collect: twigs, cotton or wool yarn cut less than 3 inches, human hair or animal fur, feathers or dried decorative grasses. Thread, plastic material and lint are the 3 big no, nos for nesting material.
  
Related Articles:
5 Tips to Attract Birds to Nest in your Bird Houses http://bit.ly/xETceZ
Common Bird House Problems http://bit.ly/wrWzyN
Which Way Do You Face a Birdhouse? http://bit.ly/AD43TW
Don’t use treated lumber to build a birdhouse http://bit.ly/x2pIG0
When do birds begin nesting? http://bit.ly/wbJ3kE
DO NOT Collect Dryer Lint for the birds to use as nesting material! http://bit.ly/wC5HcO