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THE OYSTERCATCHER'S PROGRESS 

 TOWARDS MATURITY. 



J. M. DEWAR, M.D, 



Data were obtained from eleven families of Oystercatchers 

 {Hcsmatopiis o. osiralegus) of known ages observed for periods 

 ranging from birth up to the 23rd day, and from eight families 

 of approximately known ages (+ 2 days) observed up to 

 the 35th day. The locality was the basin of the River Tay in 

 Scotland, and the period covered six breeding seasons (1909- 

 1914). For identification reliance was placed on territorial 

 isolation and the recognition of routine habits within the 

 territory since it was found that handling the chicks tended 

 to cause desertion of the territory, especially as the chicks 

 grew older. Observation could not be prolonged with certainty 

 beyond the end of the fifth week as katadromous migration 

 begins at that time. 



The young Oystercatcher is nidifugous, is well covered 

 with down which matches the normal surroundings, and is 

 attended and fed by the parents for at least five weeks after 

 birth.* 



Locomotor Activities. — The young remain in the nest 

 for 1-2 days after birth, or at all events do not go more than 

 a few feet away. Walking and running are well co-ordinated 

 from birth, but muscular weakness at first interferes with 

 progression. On the ist day the wings are used as forelegs 

 in walking. Improvement is very rapid. On the 3rd day 

 the chicks run well and swim expertly. Locomotion on land 

 appears to grade into locomotion in water without attention 

 to the change of medium, at least in many cases. A tendency 

 to make independent journeys is evident in the 2nd week, 

 and by the 4th week needs to be restrained by the parents, 

 especially as regards swimming and invasion of other territories. 



Preliminary attempts at flight are seen about the 5th day 

 as wing-flapping and leaping. Thereafter the wings are 

 frequently exercised every day until actual flight becomes 

 possible about the end of the 4th week. At first the chick 

 shows no regard for the direction of the wind, but experience 

 that facing the wind in taking off increases the lift is fixed 

 in the 3rd week and therefore well before real flying is possible. 

 Once this happens, flights become frequent partly from the 



* A fact known to F. Faber {Ueber das Leben der hochnordisthen 

 Vdgel. Leipzig, 1826. Heft II., s. 208). 



