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Nov., 1919 '235 FROth4 FIELD AND STUDY Association of Migrating Wade?.--Mention of collecting a male and female of the Baird Sandpiper by L. E. Wyman in the $uly-August CoN?oR (p. 172), calls to mind ob- servations made by myself on migrating shore birds on the Atlantic coast during recent seasons. It was early noticed that the first birds to come south in the fall as well as the late ones travelling north in the spring, were very often seen two together. At times they appeared to be male and female, which is quite possible to determine in some species without taking specimens, the female being so much larger and longer billed. At other times they looked just aiike. At first I took it for granted that these birds were mated pairs, but more recently I.have COme to h?ve little confidence in that hypothesis. Too often have a couple of boon companions, separated from the crowd and evidently counting a good deal on one another's society, been of different species, a Least and a Semipalmated Sandpiper or even a Ringneck Plover and one of the smaller species. It also appears that three birds travel in company as? often as two, perhaps more often in the late summer, and my belief is that these associations are, in general, purely platonic. We know that there are times when we prefer to travel with one or two chosen com- panions rather than with a crowd, and the more I see of them the more comparable to our own the sociai instincts of the shore birds appear. This point of view does not rest on su/ficiently definite data to be called a scientific observaton, but nevertheless I would like to present it for consideration.--JoHN T. NICHOLS, NeW Yor? City, August 15, i9i9. White-throated Swift in Contra Costa County.--On the left hand side of Pine Can- yon, Contra Costa County, about a mile above Ford's P,?nch, which is at the entrance to the canyon, are some large recks containing various ledges and cracks. While passing through the canyon on $uly 5, 1919, I noticed several White-throated Swifts (Aeronautes mela?oleuc?) sailing about these rocks. I therefore climbed up to see if their nesting site wa? accessible. I managed, with stocking feet and sm?ll finger holds, to climb up the face o the rock to an aimost inaccessible pla?e, wh.ere two big rocks come together. In this crack was an unoccupied nest situated on a small wedged-in stone. Four feet above this nest was another which was occupied, as the old bird was' flushed. While trying to decide which was the best way to reach this nest, the old bird came back at full speed and swooped up to it almost hitting me in the face. This proves that they do no[ always slow down in their speed when entering the nest. A/ter some delicate climbing and balancing, the nest was reached and found to be empty. But right above it, in a smail crack, were two young birds almost really to fiy. After trying to poke them down with a small stick I had to give it up as the little birds squeezed farther in the crack. There were more nests elsewhere in the ,rocks, as about thirty birds were observed sailing back and forth over the canyon.--LUTH?,R I?ITTLE, California Acac?emy of ?cie?ces, ?a? Francisco, California, August ?6, 1919. Luck.--If the writer had not been pessessed of a certain amount of this "article" these notes would not have been written. Briefly told the facts are these. A certain pair of Nuttall Woodpeckers (Dryobates nttttalli) chose a partly decayed fence post for a building site. The same location had been selected by a family of bum- ble-bees. The woodpeckers started near the top of the post and drilled their excavation downward, while the bees started some two feet below and burrowed upward. The two openings met and the' woodpecker remained in possession. It so happened that Mrs. Woodpecker laid a runt egg which promptly slipped into the trap nest provided by the bumble-bee, and at the time the writer examined the post the smail end of the woodpecker egg was protruding 'from the opening of the bumble-bee excavation, fully a foot below the bottom of the woodpecker's nest. In the woodpecker's dug-out were four normai eggs. If the runt had been slightly smaller, if the bumble-bee hole had been slightly larger, or if the egg had lodged or 'broken in its winding journey through the tunnel of