18- 



ORNITHOLOGIST 



[Vol. 10-No. 2 



sufficient, even before the maximum, to stnrt the 

 migratory tide. 



On tlie day following the maximum there are 

 few records, indeed scarcely more than for tlie 

 minimum nights, so that when we consider that 

 probably one half or more of these records are of 

 birds that came on some i)re\ious night, we see 

 how little movement normally occurs on this 

 night. We cannot say that no migration ever oc- 

 curs, for wc have two positive records of such 

 occuri'ences last Spring at St. Loiiis. 



To recapitulate, the greatest movement takes 

 place on the nights of maximum heat; the next 

 greatest on the night before the maximum; very 

 little on the night after, and still less, iu a 

 large number of notes only about twelve or fif- 

 teen per cent, on the niininnim night of the cold 

 wave. 



Let us turn now to a concrete example and 

 study the effect of the almospheric waves on the 

 movements of tli(^ Purple Martin. So far as last 

 winter's observations go. this species was not 

 fimiid in our (listri<l diiring tlie cold of .lanuary, 

 nor of the gnalrr jiarl ot February. Contrary to 

 the ordinary nde, the advance was about the 

 same lime in the west as in the east, as if the birds 

 were invading otir district by land from Mexico. 

 The first arrivals came to 3122 Texas, February 

 351 h; four days later they were heard by Mr. 

 Kagsdale at 33^6 Texas, while on the afternoon of 

 March iith, at 34ii Indian Territor}', I was hur- 

 riedly brought to the door by the sound of their 

 twittering around a neighbor's house. 



In Louisiana the first one is reported at '2'J^^ 

 February 23d, and in Mississippi at 341" Jlm-ch 

 1st. These bii-ds were a few stragglers that had 

 gone far ahead of their fellows. I saw no more 

 at Caddo until Jlarcli lltli, nor is any increase 

 noted from either Louisiana or ^lissi.^sippi until 

 about the siUiie dale. 



During the night of March lOtli, there was a 

 sudden and very pronounced warm wave in the 

 Mississippi Valley, marked by a strong south 

 wind. Its inrtuence was fell almo.st .simultaneou.s- 

 1_V from Bismarck, Dak., to Vick.sburg, Miss., 

 raising the temperature about twenty degrees. 

 This marks the first advance within our territory. 

 New birds come to 34" Indian Territory, fresh 

 arrivals are noted from 295' Louisiana, and the 

 first ones from 338-I Mississippi, and 3536 Arkansas. 

 But this auspicious start was to receive a severe 

 check; the next night the temperature fell thirty- 

 two degrees at Omaha, and in the northern part 

 of the valley even to zero. A halt was called and 

 the Martin rested on their arm.s — or wings. 



Slight ^N'ann waves occurred after this, and 



even quite a pronoimced one on the 16th, but the 

 Martins did not heed them; it is not until the 

 wave of the 25th that we find another note. This 

 wave, though slight, carried them forward, and 

 the next morning they are noted from the stations 

 in southwestern Missouri at 36='' and 31"^. 



The night of the 22d, a warm wave started tiom 

 the Rocky Mountains and reached Vicksburg the 

 24th. It did not have much effect in the north, 

 but gaining force as it went, in the southern 

 Mis.sissippi Valley it raised the temperature to the 

 highest of the year. The commander-in-chief of 

 the Martins ordered an immediate advance, and 

 morning light on March 25th found the picket 

 line stretching almost due east an<l west from 

 39« Illinois to 3912 Kansas. Again a halt is 

 called for about a week. 



There was a warm wave the night of the 2Ttli, 

 preceded at St. Louis by much movement among 

 other species on the 26th. There is no record 

 from any station for this wave mde.ss the two 

 records for 413«and 413«Iowa, on the •amh,bel(mg 

 here, Init it is probable that at this time they were 

 passing over northern Missouri and central Uli 

 nois, where to our great regret, we have no ob- 

 servers. At the most this could have been but a 

 slight movement, and is followed by a greater, 

 sinuiltaneous with the atmospheric wave of March 

 30th and 31st. This brings numbers of Martins 

 to all the country from 39' to 42% but marks no 

 advance beyond the limit attained li,\- the preced- 

 ing wa\'e. 



April 3d. in the upper Mississippi N'alley was 

 almost the warmest of the year, and tempted one 

 adventurous Martin to fly two hundred miles be- 

 yond his proper limits, to Lanesboro, Minn., 

 43'''' only to leave immediately, nor were any 

 more seen for eleven days. 



The first two weeks of April were for the most 

 part cloudy and cold, with occasional snows, .so 

 that it is nothing .strange that we find no advance 

 recorded. The maximum of the first warm wave 

 was in the upper Mis.si.ssippi, .\iiiil 13tli. and the 

 observations agree very well with this maximum. 

 There are a few notes one and two days jirevious, 

 as if some of the restless ones had a premonition 

 that warm weather was coming, and wished to 

 be ahead of their companions. The van is now 

 brought fairly to 43'" Minnesota and 43'»> Wiscon- 

 .sin, with large arrivals at various points south to 

 St. Louis, Mo., and ^lanhattan, Kans. The 

 wave of the night of the 17th. brings the temper- 

 ature at St. Paul for the first lime above 50' and 

 as a consequence, Martins are i-eported from four 

 stations in that vicinity, with a corresponding ad- 

 vance in Wisconsin to about 443".% 



