Jan. ISDO.j 



AND OOLOGrST. 



3 



from Arizona (Pima Co.). iiro tlio smallest of 

 any. which I have mea.sured. 



Amonjj owls, I have examples of two species 

 — the Little .SeTeech {Sraps asii,) and the 

 Barred Owl {Si/rnium nehnlosinn). With the 

 former, effffs from Texas ai-e the smallest, in- 

 ereasin<; iu size to Iowa and Hliode Island, 

 those from the latter state heino- the largest. 

 The rar. hc)i<liveii of the Pacific slope, like 

 those of other Jinpfores from the same locality, 

 persist in heinj; smaller than eastern eoj-s. and 

 ill this ea.se are inferior to Hliode Island spec- 

 imens and oiilv a trifle lar<iei- than the exam- 

 ])les cited from 'i'exas. 



Of the PicUloi I have hut a sinole instance, 

 that of a Downy Woodpecker {Drt/ohafes pu- 

 he.Hcens). in which the lim.ited data ogives the 

 maximum to Xew England, while western e.<j<;s, 

 usually the largest, are in tliis case the smaller. 

 The ComTnon Crow (CnrvuH aDieriraiiits), 

 among the C'ormxJw has a maximum in Califor- 

 nia s])ecimens, and a minimum in the small 

 Floridanian variety, with Xew Brunswick and 

 Rhode Lsland eggs coming in between, with a 

 slight diflerence in size favoring Rhode Island 

 eggs, due perhaps to the large numhcr 

 examined. 



In the family TcterkJce, eggs of the Meadow 

 Laik {Stnrnf^U(( imtr/na) are largest in New 

 i:ngland. and those of .Minnesota and Illinois 

 are even inferior to var. tiKwicKua from Texas, 

 nnd the eggs of the Crow Blackbird (Qiiiscalus 

 f/iiiarida) and its mr. cenens, show a like varia- 

 tion. Orchanl Orioles' eggs from Rhode 

 Island and those from Texas average the same. 

 Michigan .specimens are a little smaller. 



With the Frhit/illithe the general lule holds 

 uniformly good, and two examples will be 

 sufficient. Eggs of the S(mg .Sparrow (Melo.y- 

 j)iz(( fasdafd) in Massachusetts are much 

 smaller than those of rar. uitttata of Oregon, 

 and tho.se of the Chii)ping .Sparrow (Spizella 

 domestlca) increase from Massachusetts to Ver- 

 mont and Minnesota, reaching the maximum 

 in eggs of vni-. uriznmf of California. 



Although my data for the swallows is inex- 

 tensive, the little there is conforms to the 

 general rule, as in the case of the Cliff .Swallow 

 (PetrnrhelUhin lunlfrons), in which the eggs 

 from Illinois average .70 and Xew P:r.gland 

 specimens, .(Wi. 



Of the Ldtiida- the eggs of luaovicianxx 

 proper from Florida measure aliout .SO of an 

 inch, while those of rar. f.n'u1>it(iri<lt'.^ taken in 

 C'alifornia measure .8(5. 



Specimens of eggs of the Blue-headed Vireo ' 

 (T7rco .wlifarhi.i) average .(ili in .Massachusetts. ' 



are a trifle smaller in the Coloiado variety, and 



reach the greatest size in var. cas.sini of Oregon. 



Of the SylricoUdie, two examples are all 



that I am able to give. In specimens of the 



eggs of the Chestnut-sided Warbler from 



' Maine and Massachusetts, there is a difference 



in size in favor of the former state, while in 



the Icferhne, eggs of /. r/rPH.s from Rhode 



Island are larger than those from Pennsylvania 



i and eggs of tlie nir. lotrjirmtda from Arizona 



are smallei-. 



One example of the genus HarporhynchuK.^ 

 that of H. riifm, the most widely distributed 

 species, is all that is available at the present 

 time. Minnesota specimens are largest, meas- 

 uring .91, while eggs from Rhode Island aver- 

 age .90, and those of the rar. lomiiroHtrlH from 

 Texas meixsure but ..'^(i. 



Among wrens, the common axlnn is the only 

 example that I liave obtained. Eggs of the 

 House Wren {Trn(/lodyte,<i (edon) from Iowa, 

 Illinois and Rhode Island present a uniform 

 average measurement of ..5S. Those of rar. 

 parkinani of Califoinia are a trifle larger. 



Of the ParUhf, tlie eggs of the Chickadee 

 {Pant.s afrirai>llhis) in Rhode Island and the 

 rar. arcidcufalin of Oregon present the .same 

 average, but eggs of the tyi»e from Illinois are 

 somewhat .superior in size. 



In the Pnlioi>fid:v the average mea.surement 

 of eggs of cceriilea in New Jersey and var. 

 plumbea of Arizona are alike, but eggs of the 

 type from Texas and Mississippi are smaller. 



The thrush family is represented by two 

 species of as many genera, the Hylochichlldce 

 and Merttiklce. The former is represented by 

 ustnlata and its var. Hwalnsoni, specimens of 

 the type averaging .78 of an inch in Oregon, 

 and .74 in California. Eggs from (rrand Ma- 

 nan average the same as tiie latter. 



In the genus Mernla, eggs of the Robin aver- 

 age alike in Minnesota and Michigan, while the 

 western variety from California are larger. 



Thus we find that a series of measurements 

 of the eggs of twenty-seven species of birds 

 show a decided and generally uniform varia- 

 tion in size, becoming larger in an advance 

 from south to north, and from east to west. 



Reviewing first the variation of northern and 

 southern specimens, we find that the rule of 

 variation, as established by Baird, is much 

 more uniform among birds that are least devel- 

 oi)ed, say birds as low as the raptores and 

 lower in the scale, and is also frequent among 

 a few non o.^cine.s which are more highly devel- 

 oped, but ill l»irds highly organized, excepticms 

 are mudi more fre(jueiit. 



