Updated June 1st: First day postmarks:
Standard 4-bar FIRST DAY OF ISSUE
Digital Color Postmark:

from the Postal Bulletin May 27th:
On June 1, 2015, in Kansas City, MO, the U.S. Postal Service® will issue the Coastal Birds Postcard Rate stamps (non-denominated priced at 35 cents), in four designs, in a pressure-sensitive adhesive (PSA) coil of 100 stamps (Item 783500) produced by Ashton Potter, and also a pane of 20 stamps (Item 117600) produced by Sennett Security Printers.

The stamps will go on sale nationwide June 1, 2015.

With the release of the Coastal Birds postcard stamps, the U.S. Postal Service celebrates four eye-catching birds: the red knot (Calidris canutus), king eider (Somateria spectabilis), roseate spoonbill (Platalea ajaja), and magnificent frigatebird (Fregata magnificens). The stamps feature highly stylized, digital portraits of each bird. The word “POSTCARD” on the stamps indicates their usage value. Like Forever® stamps, these stamps will always be valid for the rate printed on them. The initial price and value for these stamps is 35 cents. Art director Greg Breeding designed the stamps with artwork by Tyler Lang.

How to Order the First-Day-of-Issue Postmark:
Customers have 60 days to obtain the first-day-of-Issue Postmark: by mail. They may purchase new stamps at their local Post Office, at The Postal Store® website at http://www.usps.com/shop, or by calling 800-STAMP-24. They should affix the stamps to envelopes of their choice, address the envelopes (to themselves or others), and place them in a larger envelope addressed to:

35¢ Coastal Birds Stamps
Cancellation Services
8300 NE Underground Drive, Pillar 210
Kansas City, MO 64144-0001

After applying the first-day-of-Issue Postmark:, the Postal Service will return the envelopes through the mail. There is no charge for the postmark up to a quantity of 50. For more than 50, customers have to pay five cents each. All orders must be postmarked by July 31, 2015.

There are two philatelic products for the Coastal Birds PSA coil of 100 stamps issue:

• 783516, First-Day Cover, 2 of same bird (set of 4), on each, $4.56.
• 783521, Digital Color Postmark, 2 of same bird (set of 4), $7.40.

There are seven philatelic products for the Coastal Birds pane of 20 stamps issue:

• 117606, Press Sheet with Die-cut, $70.00 (print quantity 250).
• 117608, Press Sheet without Die-cut, $70.00 (print quantity 500).
• 117610, Digital Color Postmark Keepsake, $14.95.
• 117616, First-Day Cover, 2 of same bird (set of 4), $4.56.
• 117621, Digital Color Postmark, 2 of same bird (set of 4), $7.40.
• 117631, Stamp Deck Card, $0.95.
• 117632, Stamp Deck Card with Digital Color Postmark, random 2 of same bird, $2.20.

Technical Specifications:

Issue: Coastal Birds Stamps (coil)
Item Number: 783500
Denomination & Type of Issue: Postcard Rate Non-Denominated, Mail-Use
Format: Coil of 100 (4 designs)
Series: N/A
Issue Date & City: June 1, 2015, Kansas City, MO 64108
Art Director: Greg Breeding, Charlottesville, VA
Designer: Greg Breeding, Charlottesville, VA
Typographer: Greg Breeding, Charlottesville, VA
Artist: Tyler Lang, Portland, OR
Modeler: Joseph Sheeran
Manufacturing Process: Offset, Microprint
Printer: Ashton Potter (USA) Ltd. (APU)
Printed at: Williamsville, NY
Press Type: Muller A76
Stamps per Coil: 100
Print Quantity: 600 million stamps
Paper Type: Nonphosphored Type III, Phosphor Tag applied
Adhesive Type: Pressure-sensitive
Processed at: Ashton Potter (USA) Ltd. (APU)
Colors: Black, Cyan, Magenta, Yellow
Stamp Orientation: Vertical
Image Area (w x h): 0.70 x 0.84 in./17.88 x 21.34 mm
Stamp Size (w x h): 0.84 x 0.98 in./21.43 x 24.89 mm
Coil Size (w x h): 84.38 x 0.98 in/2143.13 x 24.89 mm
Plate Size: 768 stamps per revolution
Plate Numbers: “P” followed by four (4) single digits
Coil Number Frequency: Plate numbers located under first stamp of impression

Technical Specifications:

Issue: Coastal Birds Stamps (pane)
Item Number: 117600
Denomination & Type of Issue: Postcard Rate Non-Denominated, Mail-Use
Format: Pane of 20 (4 designs)
Series: N/A
Issue Date & City: June 1, 2015, Kansas City, MO 64108
Designer: Greg Breeding, Charlottesville, VA
Art Director: Greg Breeding, Charlottesville, VA
Typographer: Greg Breeding, Charlottesville, VA
Artist: Tyler Lang, Portland, OR
Modeler: Donald Woo
Manufacturing Process: Microprint, Offset
Printer: Banknote Corporation of America/SSP
Printed at: Browns Summit, NC
Press Type: Alprinta &$
Stamps per Pane: 20
Print Quantity: 200 million stamps
Paper Type: Phosphor Tagged Paper, Overall
Adhesive Type: Pressure-sensitive
Processed at: Banknote Corporation of America, Browns Summit SC
Colors: Cyan, Magenta, Yellow, Black
Stamp Orientation: Vertical
Image Area (w x h): 0.73 x 0.84 in./18.54 x 21.33 mm
Overall Size (w x h): 0..87 x 0.98 in./22.10 x 24.89 mm
Full Pane Size (w x h): 5.3 x 4.88 in./134.62 x 123.95 mm
Press Sheets Size (w x h): 10.6 x 22.4 in./269.24 x 619.76 mm
Plate Size: 200 stamps per revolution
Plate Numbers: “S” followed by four (4) single digits
Marginal Markings: Front: Plate numbers in four corners of pane
Back: © 2015 USPS • USPS logo • Plate position diagram • Barcode (117600) in upper right and lower left corners of pane • Promotional text

From the USPS May 26th:
With the release of the Coastal Birds postcard stamps, the U.S. Postal Service celebrates four eye-catching birds: the red knot (Calidris canutus), king eider (Somateria spectabilis), roseate spoonbill (Platalea ajaja), and magnificent frigatebird (Fregata magnificens). The stamps feature highly stylized, digital portraits of each bird. These Forever stamps will always be equal in value to the applicable price for the price category printed on them at the time of use. The initial price and value for these stamps is 35 cents. The Coastal Birds stamps feature the art of illustrator Tyler Lang of Portland, OR. Greg Breeding of Charlottesville, VA, was the art director.

The word “POSTCARD” on the stamps indicates the usage value. The postcard price is effective May 31.

Updated May 18th, from the USPS:
With the release of the Coastal Birds postcard stamps, the U.S. Postal Service celebrates four eye-catching birds: the red knot (Calidris canutus), king eider (Somateria spectabilis), roseate spoonbill (Platalea ajaja), and magnificent frigatebird (Fregata magnificens). The stamps feature highly stylized, digital portraits of each bird. The word “POSTCARD” on the stamps indicates their usage value. These Forever stamps will always be equal in value to the applicable price for the price category printed on them, at the time of use. The initial price and value for these stamps is 35 cents. Art director Greg Breeding designed the stamps with artwork by Tyler Lang.

The first day of issue is June1, without a ceremony. The city is Kansas City (Stamp Fulfillment Services).