NATURAL HISTOHY OF THE KING RAIL 



63 



Both sexes incubate. To prove this, one night between 9 and 10 p.m., 

 I placed white paint in a small can 'at the end of a long stick and 

 poured it on the backs of incubating birds at two nests. On subse- 

 quent visits to the nests, unmarked birds were often seen incubating. 



Table 10. — Weight loss in three King Rail eggs during incubation 



[In grams] 







Weight on — 







Day 1 



Day 7 



Day 14 



Day 21 



Egg 1 



Egg 2. 



Egg 3 



18.9 



20.3 



18. 8 



18.7 

 19.5 

 18.4 



17.8 

 18.8 

 17.5 



16.7 

 17.9 



(0 



Mean 



19.33 



18. 86 



18. 03 



17.3 



» Clutch destroyed. 



Later that season an exchange of sexes was observed at a nest 

 during the incubation period. At 5 :18 p.m. an incubating bird called 

 from the nest, whereupon its mate immediately came from the cattails 

 across the road to a point about 20 yards from the nest, and began 

 walking toward the nest until it was within 5 feet. The incubating 

 bird then left the nest and was replaced by its mate, which remained 

 on the nest for 17 minutes, when an exchange again took place. 



In another instance, when one member of an Arkansas pair nesting 

 near a road was killed by an automobile, its mate continued to incubate 

 the eggs. An incubating bird caught on a nest at 5 :45 p.m. May 16, 

 was a male. 



Incubating birds seldom flush until an intruder is within 10 feet or 

 less of the nest. As the hatching date approaches, they become more 

 tenacious. On several occasions I was able to band incubating birds, 

 but not without considerable resistance from them. On one occasion 

 when I approached a nest at hatching time, the bird flew from the nest 

 and struck me in the chest. On other occasions birds have struck at my 

 legs or have run to my feet where they remained with wings out- 

 stretched. Frequently they feigned injury by spreading the wings, 

 fluttering through the vegetation (fig. 26), and uttering a distress call 

 which might be written as a gutteral rack-k-k-, rack-k-k-, rack-k-k-, 

 sometimes varying to sound like chur-ur-ur-ur (the roll on the ur is 

 like the German "R"). Other scolding notes given by a rail flushed 

 from its nest are a resonant gip-gip-gip- and kik-kik-kik-. 



In contrast to this type of behavior, the Clapper Rail is usually gone 

 before the intruder gets near the nest. At Chincoteague, Ya., I have 

 examined some 200 Clapper Rail nests, and only on some half dozen 

 occasions has an incubating bird remained while approached to within 

 10 feet. This appears to be a striking behavioral difference between 

 these two closely related species. 



