Olson and Rauzon • WAKE ISLAND RAIL 
671 
A 
B 
C 
D 
FIG. 4. Photographs of Wake Island Rails (Gallifallus wakensis) in life. A: nest with four eggs and one recently 
hatched young; B: recently hatched young; C and D: young about one-third grown. Torrey Lyons, ca. 1939. M VZ Archives. 
and there is even slight overlap (Tables 2. 3). 
Kirchman and Steadman (2006. 2007) compared 
G. wakensis with the numerous prehistorically 
extinct species of Gallifallus described from 
Oceania with the only one that was as small in 
some dimensions being G. ripleyi (Steadman 
1987) from Mangaia. Cook Islands. The small 
land area and harsh environment of Wake Atoll, 
where food supplies are probably diminished in 
times of drought, extensive overwash, or higher 
rat populations would have provided strong 
selection factors for reduced body size, whereas 
the head would need to be sufficiently large to 
obtain and process food, and to function efficient¬ 
ly in interspecific aggressive interactions. 
Gallirullus wakensis and G. owstoni are among 
the few flightless rails to have lost the 10th 
(outermost) primary (Livezey 2003:112). The 
expected changes in the remiges, body plumage, 
and rectrices that are usually correlated with 
flightlessness were otherwise relatively minor 
(Livezey 2003: tables 27-29). The wing claw 
(unguis alularis) was noted to be disproportion¬ 
ately large in flightless rails and most notably so 
in smaller species (Livezey 2003:141), which 
accords with Wetmore’s observations that in G. 
wakensis “the wing claw in this species is very 
large and strong" (Olson 1996:184), and Lyons 
(1939. 26 Oct) that in the downy young there is a 
“prominent claw on front of wing." 
We know the Wake Island Rail was function¬ 
ally completely flightless from behavioral obser¬ 
vations, yet the skeletal adaptations associated 
with this condition are invariably moderate 
(Livezey 2003: tables 58-64). Thus, whereas 
functional flightlessness is absolute, there may 
be degrees of flightlessness in morphology. The 
extent ol modification in G. wakensis is relatively 
slight, which accords with its assumed relatively 
recent evolution. The most obvious manifestation 
in the skeleton is the reduction in size of the wing 
and particularly in the depth of the carina of the 
sternum (Fig. 5), which as Wetmore noted “is 
very low and the breast muscles slight " (Olson 
