cause neither is strongly vociferous in migration. The 
ags are not loud, and as Traill’s flycatchers are late 
ring migrants, arriving when many other species are in 
I song, there is a good possibility that Traills’ songs are 
en “covered up.” However that may be, the vast 
jority of Empzdonax seen are not singing, and cannot 
assigned a specific population identity. If, for 
ample, we state that the more northern-ranging alder 
catcher is a later spring migrant than the local 
seding willow flycatcher, the statement does not take 
© account the possibility that the silent Empidonax 
ild be predominantly alders. 
Prior to now the Illinois literature has treated the 
aill’s complex as one species (see explanation of recent 
ssification in the introduction of this report), and very 
y authors who discussed Traill’s flycatchers mentioned 
'song form. In our discussion, we also treat the 
nplex mainly under the name of Traill’s flycatchers, 
1 the reader must bear in mind that two very closely 
ated species are included. 
Traill’s flycatchers of both species are known to be 
ht migrants in Illinois. Arrival of Traill’s flycatchers in 
nois as early as April 24 (Musselman 1934-1935) is 
WINTER 
. 
| mites 
ig. 33. — General distribution of Traill’s flycatchers. The outlined 
May include large sections in which populations of the species are 
T even absent because of the nature of the terrain and paucity of 
le habitat. The ranges of the two species of Traill’s flycatchers are 
y known. The two are sympatric at least in places along the 
le-shaded band. 
probably exceptional, and even April 29 (Widmann 
1907, Fawks 1956) is early for the species. The earliest 
spring specimen we’ve examined (U.S. National Museum 
No. 108366), from Warsaw in central Illinois, was taken 
May 3 and is a willow flycatcher. Widmann (1907) found 
Traill’s flycatcher to be very regular in its appearance in 
the St. Louis area on May 4 or 5. We suspect that the 
early arrivals are likely to be willow flycatchers. Most of 
the Traill’s population, however, arrives after May 12 in 
southern Illinois, and after May 20 in central and 
northern Illinois (Fig. 34). 
The spring migration of Traill’s regularly extends well 
into June, and possibly into July, even in the south (Fig. 
34). The consistent peak in numbers of Traill’s 
flycatchers in the three regions in early June (Fig. 34) 
includes local breeding birds (willow flycatchers) and 
probably also passing transients of both the “fitz-bew” 
(willow) and “fee-bee-o” (alder) song forms. In the St. 
Louis area both forms have been heard in May, the 
alders being present only about a week while passing 
through, with the willow flycatchers remaining 
throughout the summer (Jones 1953). James Funk 
(personal communication) has heard the alder song in 
southern Illinois (Union County) on May 20, and in 
central Illinois on May 28 (Adams County) and June 3 
(Champaign County). Robert Russell has observed that 
the willow flycatcher usually arrives in northern Illinois 
by the second week in May, while the (singing) alders 
arrive about the end of May and reach peak numbers 
June 6-8, when Russell heard as many as six singing 
(Kleen & Bush 1971a). An alder which we found in 
Iroquois County on June 22 appeared to be on terriotry 
but subsequently disappeared, leaving only nesting 
willow flycatchers in the area. This June 22 record may 
not be particularly late migration in Illinois for either 
population, as we have recorded willow flycatchers 
arriving on nesting territories in early July in east-central 
Illinois. We also have a female specimen of the alder 
flycatcher (INHS #7) taken June 25, 1967 in central 
Illinois. 
In summary, the spring migration of willow 
flycatchers in Illinois lasts from about May 1 to July 1, 
and the migration of alders from as early as May 20 into 
July. 
Distribution 
The general distribution of Traill’s flycatchers is 
shown in Fig. 33. The alder flycatcher is the more 
northern-ranging of the two species and the willow 
flycatcher the more southern- and western-ranging. 
Where the breeding ranges of the two forms overlap both 
in Canada and the United States (Stein 1963) the species 
apparently retain their integrity. 
The breeding distribution of Traill’s flycatchers in 
Illinois is shown in Fig. 35. All of the nesting “Traill’s” 
which we have observed in Illinois, in all regions of the 
state and in all habitats, have proven to be the willow 
flycatcher. 
Alder flycatchers have been known to nest as close as 
EW 
