THESES. JAKOB HEGYFOKY. 



in the former case the temperature varies in degrees below and above 

 0", whereas in the latter it varies only in degrees above 0". (Term. Kozi. 

 Ann. 1900. p 89.) Prominent oscillations in temperature and arrival run 

 •parallel and vice versa. („Aquila" IV. p. 7.) 



In Hungary Birds arrive earlier in the large plains than in other 

 parts of the country, the difference according to 3 years observations 

 of 14 species being about 7-4 days. This is caused by climatic condi- 

 tions, which in spring are most favourable on the vast lowlands. 

 („Aquila" X. p. 198.) 



On Method. 



In regard to future observations Hegyfoky recommends the follow- 

 ing points. 



1. In working out data of Migration only the simultaneous ones 

 are to be used as a basis to calculate the average. 



2. In long series of observations it is necessary to examine the ave- 

 rage of shorter periods. Lustres and Decennaries, with regard to their 

 accuracy and variation, otherwise it would be impossible to use for 

 comparison the average of observations that are not simultaneous. 



3. Even single dates are valuable, because they are adaptable for 

 correcting errors in the series. 



4. In publications the year should stand first; the species ought to 

 be arranged alphabetically. 



5. The average of a period should be calculated from the total data 

 of one period; the earliest arrival should be marked : * ; the latest +, or 

 with conspicuous letters. If the number of data is very bulky, pentade- 

 rates should be established, in order to determine precisely the begin- 

 ning, culmination and end. 



6. There should be 4 to 6 stations for observation of as many 

 species as possible, besides numerous stations for observations of a few 

 specially characteristic species. The localities should be published alpha- 

 betically. 



BZi 29 izi 



