Use of Song Types by Mountain Chickadees (Poecile gambeli)

8 Pages·1999·4 MB·English

by  Myra O Wiebe

Wilson Bull., 111(3), 1999, pp. 368-375
USE OF SONG TYPES BY MOUNTAIN CHICKADEES
{POECILE GAMBELI)
MYRA O. WIEBE'- AND M. ROSS LEIN' ^
—
ABSTRACT. We investigated the composition and function of individual song repertoires in Mountain
Chickadees (PoecUe gambeli) in Alberta, Canada. Individual males had repertoires of 4—7 song types, but three
types made up 90% of all songs. We tested and rejected the hypothesis that all song types convey the same
behavioral messages. Different song types were associated with different behavioral situations. Males used 3-
note songs predominantly during undisturbed singing and 2-note songs predominantly during non-aggressive
activity. Three-note songs with each successive note lower pitched were associated with male—male interactions.
We suggest that different song types convey messages indicating different levels of aggression by the singer.
The function of individual repertoires in Mountain Chickadees appears to be similar to that of other North
American chickadees and titmice, with different song types having different communicative functions. Received
7 Aug. 1998, accepted II Feb. 1999.
Although individuals of some species of contrast, other species, such as the Blue Tit
songbirds sing only one type of song (Searcy {Parus caeruleus), the North American tit-
1983), males of many species possess reper- mice {Baeolophus), and some of the North
toires comprising a number of discrete cate- American chickadees {Poecile), seem to pos-
gories of songs, or song types (Dodson and sess song types that convey different messag-
Lemon 1975). The significance of song rep- es (Smith 1972, Dixon and Martin 1979, Gad-
ertoires has been the subject of much research dis 1983, Schroeder and Wiley 1983, Bijnens
and speculation (reviewed by Krebs and and Dhondt 1984, Johnson 1987).
Kroodsma 1980, Kroodsma 1982, Kroodsma We examine the role of individual reper-
and Byers 1991, MacDougall-Shackleton toires of Mountain Chickadees {Poecile gam-
1998). beli). Mountain Chickadees sing relatively
Most species of the genera Parus, Poecile, simple songs consisting of 2-6 whistled notes,
and Baeolophus have individual song reper- with any number of these notes shifted to fre-
toires (Hailman 1989), although the role of quencies lower than the others (Hill 1987).
repertoires appears to differ among species Song types are defined easily by variation in
[these closely-related genera were formerly number and pitch of notes; individual reper-
lumped as Pcirus (American Ornithologists’ toires consist of 3-5 song types (Hill and Lein
Union 1997)]. Individual male Great Tits {Pa- 1989). Although no studies have investigated
rus major) may use different song types in whether Mountain Chickadees can differenti-
sequence with no apparent change in the ex- ate among song types, this seems probable be-
ternal situation (Hinde 1952), suggesting that cause closely related Black-capped Chicka-
all song types convey the same messages. dees {Poecile atricapillus) distinguish among
Consequently, Great Tits have been used to songs varying in note number and pitch (Rat-
test many of the hypotheses that suggest that cliffe and Weisman 1986; Weisman and Rat-
overall repertoire size is important (e.g., Krebs cliffe 1989).
1976, 1977; McGregor et al. 1981; Baker et We documented song variation and singing
al. 1986; Lambrechts and Dhondt 1988). In behavior of male Mountain Chickadees during
the breeding season. Our null hypothesis was
Divi.sion of Ecology (Behavioral Ecology Group), that all song types of the Mountain Chickadee
Dep't, of Biological Sciences, Univ. of Calgary, Cal- convey the same behavioral messages, and
gary, Alberta T2N 1N4, Canada; thus the song type that a male sings would be
E-mail; [email protected] independent of the situation in which it is
2 Present address: Canadian Wildlife Service, Suite used. The alternate hypothesis was that song
301, 5204 50th Avenue, Yellowknife, Northwest Ter- types convey different messages and thus cer-
ritories XI A 1E2, Canada; tain song types would have a higher proba-
E-mail; [email protected].
Corresponding author. bility of being sung in specific situations.
’
368
Wiehe and Lean • SONG TYPES OF MOUNTAIN CHICKADEES 369
METHODS
gaged in other activities); b. engaged in non-aggressive
(51T°h0e0'stNu,dy 1w5a°s00'coWnd)ucotfetdheatUntihveerBsairtryieorfCLaalkgearsyi’tse eatcct.i)v;itci.esen(ge.agg.,edfoirnagaignggr,e.spsrieveeniancgt,ivifteieesdi(nig.e.necsotulnitnegrs-,
tfKhoaerneasRntoaiscnkkhiyasbiMIFtioeedulndbtyaSitManotsuionontsfaiisnnoutCthhehiwcKekasantdaeenreansskAiilssbdeorVtmaali.lneayTtheoedf sasiiwtnaigoyinnfgornowimttehrtrhieotronrecy.:hstasas.iitnewg.it(th3eir)nriLt5ooc0riaatmliononefiogtfhhbemoarntsee)s:.t a(s.2i)tper;Peosb--.
by trembling aspen (Populus tremuloides), white ent in the vicinity of the singer; b. absent from the
vicinity. Each song was assigned to a particular situ-
spruce (Picea glaiica), and lodgepole pine (Pinus con-
ation. Ifthe situation changed while the male was sing-
torta). Mountain Chickadees are secondary cavity-
ing, then songs recorded before the change were as-
nesters, using pre-existing cavities such as natural signed to the first situation, and songs recorded after
crevices or deserted nests of other cavity-nesting birds the change assigned to the second situation. Nests of
(Hill 1987, pers. obs.). In southwestern Alberta, Moun- six pairs were found, allowing us to also assign songs
tain Chickadees start to search for suitable nesting cav-
for these males to particular breeding stages (nest
ities during April (Hill 1987, pers. obs.). Nest-building
search/build, egg-laying, incubation, or nestling).
occurs in early May. Incubation starts near the end of Mountain Chickadees often were out of sight when
May and lasts about 14 days. The nestling period gen- in the tops of coniferous trees. We assumed that songs
erally lasts 18-21 days (Dahlsten and Copper 1979) given during such intervals were in the same situation
but may be as short as 14 days (pers. obs.). Nestlings as the last song given prior to disappearance. However,
fledge during the last week in June and early July. if a subject was out of sight for more than 5 minutes,
Mountain Chickadee songs, and information on the we recorded its behavior for that interval as unknown.
situations of song use, were recorded from April to We categorized different song types by variation in
July 1993. Data were collected from 1 1 males, of number of notes and relative pitch of notes within a
which 7 were marked with a unique combination of song. These two features showed the most obvious
colored plastic leg bands. We could identify unbanded variation among songs and were relatively easy to dis-
males because males in adjacent territories were band- tinguish by ear. We confirmed these classifications by
ed; we also used territorial location, use of favorite examining audiospectrographs of many songs using
singing sites, or association with a particular nest cav- SIGNAL bioacoustical analysis software (Engineering
ity to identify unbanded males. All males except one Design, Belmont, Massachusetts). Transcriptions ofre-
foraged frequently with one other Mountain Chickadee cordings were made using OBSER'VER software (Nol-
and therefore were presumed to be mated. Because dus Information Technology, Wageningen, The Neth-
Mountain Chickadees defend their entire home range erlands).
(Hill 1987), we determined the extent of a male’s ter- We examined separately the relative importance of
ritory by noting areas in which he was found regularly. number ofnotes in a song and the pitch ofnotes within
Observations of aggressive interactions between males a song. To determine the influence ofnumber ofnotes,
helped to confirm the locations of territorial boundar- we combined all song types with the same number of
ies. notes regardless of the pitch of the notes within the
It was impossible to sample songs of all individuals song. Statistical tests were performed only for 2-note
in one day, but usually each individual was observed and 3-note songs because sample sizes for songs with
at least once in a three-day period. Observations oc- 1 note and 4 notes or more were too small. To examine
curred between 04:00 and 12:00 (MST), the period the influence of pitch, statistical tests were performed
when chickadees are most active. An observation pe- only for “common 3-note songs’’ and “descending 3-
riod began when a male started to sing and lasted from note songs” (see descriptions in Results). Sample sizes
a few minutes to over an hour, depending on how long of other song types with variations in pitch were too
the individual sang. Songs and verbal descriptions of small for statistical testing.
the different elements of the situation during singing If different song types are not used in different sit-
were recorded onto Sony C-90HF cassette tapes using uations, one would predict that a particular song type
AKG D190E or Sony ECM-33P microphones, Sony should occur in a specific situation at the frequency
PBR-330 parabolic reflectors, and Sony TCM-5000 or expected if song types are used at random. To examine
SonAlylTrCecMo-rd5i0n0gs0EweVretapmeadreecobrydeerist.her MOW or a field Xt'hevianlfuleusenfcoer o2fXno2te cnounmtbiengrenicnysotnagbsl,eswoef ceailtchuerlattehed
assistant. Before worMkiOngWindependently, the field as- relative number of 2-note songs and all other song
sistant accompanied during 15 observation pe- types compared between specific situations of use, or
riods to ensure that both observers were making com- the relative number of 3-note songs and all other song
parable observations. We did not notice chickadees en- types compared between specific situations of use. To
gaging in behaviors directed at the observer during any examine the influence of pitch in songs, we calculated
ofthe observation periods, so we believe that the effect values for 2 X 2 contingency tables of the number
of our pre.sence was minimal. of common 3-note songs and descending 3-note songs
We
recorded three elements of the situation while compared between specific situations of use. The in-
males were singing. (1) Behavior of the singer: a. un- dependent event in all contingency tables was a single
disturbed (i.e., singing while stationary and not en- song.
370 THE WILSON BULLETIN • Vol. HI, No. 3, September 1999
A B
We conducted a separate contingency analysis for 6-
each individual for every situation of use. We were not
able to record all individuals in different situations.
4-
Consequently, the number of individuals used in each
comparison varied from four to seven. We combined
the results of individual contingency analyses using a N. 2-1 1 -T 1 1 1 H
test described by Cochran (1971:151). This test ac- X
counts for differences in direction of response among ^ 6- C D
individuals and can be used even if there is a wide
range of sample sizes and probabilities among individ- o
C 1
uals. The test calculates a z-value that can be compared 0) 4-
3
to the normal distribution to determine significance,
O"
with non-significant results indicating that the song Ok’ 2O.-
types are independent of the situation of use. The sign U-
of the z-value indicates the direction of deviation from 6- E F
the expected.
Most statistical tests were performed using STATIS-
m m m
TIX 3.5 for Windows (Analytical Software, St. Paul, 4-
<
Minnesota). Differences at an a 0.05 were consid-
ered to be significant.
2- 1 1 1 1 j 1 1 ’"'I 1 1
RESULTS
Time (seconds)
—
We
Composition of song repertoires. re- PIG. 1. Audiospectrograms of song types most
corded an average of 1,501 songs (± 435 SE; commonly used by Mountain Chickadees on the study
range = 222-4,372) from each of the 1 1 focal area. A. Common 3-note song. B. Common 2-note
males, with an individual male being recorded song. C. Descending 3-note song. D. 2-note song with
an average of 15.1 days (± 2.2; range = 6- both notes the same pitch. E. Three-note song with all
28). Average total repertoire size was 7.4 song notes the same pitch. F. Typical 4-note song. All high-
types (± 0.3; range = 6-9). However, song qatuatlhietybergeiconrndiinnggsofofthseosnognsghathdatthies sphroerste,ntupisnwtehpetcnoomt-e
types used rarely by an individual may have mon 3-note, the common 2-note song, and the de-
been “accidental” productions rather than scending 3-note song shown in this figure.
regular elements in the repertoire. Excluding
song types that represented less than 1% of
the total songs for an individual, the average dividuals < 4% of total songs recorded were
repertoire size was 5.1 song types (± 0.3; descending 3-note songs. All other variants
range = 4-7). There was no relationship be- had frequencies of < 12% of an individual’s
tween the number of songs recorded from an repertoire, including 2-note and 3-note songs
individual and the estimated size of his rep- with all notes of the same pitch (i.e., within
ertoire (all song types: Spearman r = 0.36, P 200 Hz of one another; Figs. ID, IE) and
> 0.05, n = 11; song types > 1%: Spearman songs with four or more notes (Fig. IF). Wie-
r = -0.27, P > 0.05, n = 11), indicating that be (1995) gives details of frequencies of use
all repertoires were sampled adequately. of song types by each focal male and the use
“Common 3-note songs” (3-note songs of 2-note songs, common 3-note songs and
with the last two notes lower in pitch than the descending 3-note songs, in different situa-
first note. Fig. lA), “common 2-note songs” tions by individual males. These data are sum-
(2-note songs with the second note lower- marized in the following sections.
pitched, Fig. IB), and “descending 3-note V—ariation in song use among breeding stag-
songs” (3-note songs with each successive es. Two-note and 3-note songs were not
note at least 200 Hz lower in pitch than the used at random during many breeding stages,
previous note. Fig. 1C) were the prevalent although there was much individual variation
song types. The most-frequent song type was in the relative use of these song types within
common
common 2-note song for 5 of the 1 1 focal all stages (Tables 1, 2). Likewise,
males, common 3-note song for 4 males, and and descending 3-note songs were not used at
descending 3-note song for 2 males. All males random during different stages and there was
sang these three song types, but for three in- also much individual variation (Table 3).
1
Wiehe and Lean • SONG TYPES OF MOUNTAIN CHICKADEES 371
TABLE I. The use of 2-note songs by male Mountain Chickadees in various situations, compared to all
other song types. Columns headed “AM males” refer to combined analysis of contingency tables for individual
males. Columns headed “Individual males” indicate numbers of contingency tables for individual males with
significant departures from expectations.
Individual males
All males Preferred song type
Situation n Preferred song^ c-value p 2-note Other None
Nest searching/building stage 5 Other -6.77 <0.01 2 3 0
Egg-laying stage 6 + 1.86 0.06 3 1 2
Incubation stage 6 2-note +5.99 <0.01 3 2
1
Nestling stage 4 Other -2.30 0.02 1 1 2
Near nest 6 2-note +3.94 <0.01 4 0 2
Mate present 7 Other -2.45 0.01 1 3 3
Undisturbed singing 7 Other -9.1 <0.01 0 5 2
Male-male interaction 6 -0.22 0.83 0 0 6
“Indicate.s that 2-note songs were used significantly more frequently (2-note)orless frequently (Other)than expected in thatsituation. Ablankindicates
no significant deviation from expected frequencies.
Variat—ion in song use among behavioral sit- individuals using common 3-note songs pref-
uations. When singing near the nest site, erentially (Table 3).
males used 2-note songs significantly more When engaged in undisturbed singing, in
frequently (Table 1) and 3-note songs signifi- comparison to singing while engaged in an-
cantly less frequently (Table 2) than expected. other non-aggressive activity such as foraging,
This pattern also is reflected in the song types 2-note songs were used significantly less fre-
used preferentially by individuals. Common quently (Table 1), and 3-note songs signifi-
3-note songs were less frequent than expected cantly more frequently (Table 2) than expect-
(and descending 3-note songs more frequent) ed. Song type preferences of individuals are
when males were singing near the nest, al- entirely concordant with this overall pattern.
though there was much individual variation Frequencies of common and descending 3-
(Table 3). note songs did not differ from expectations
Males sang 2-note songs significantly less during undisturbed singing (Table 3).
frequently than expected in the presence of During male—male interactions, common 3-
their mates, as indicated by the combined note songs were used significantly less fre-
analysis and by the preferred song types of quently, and descending 3-note songs signifi-
individuals (Table 1). Common 3-note songs cantly more frequently, than expected (Table
were used significantly more frequently than 3). Three of five males showed significant
expected in this situation, with five of seven preferential use of descending 3-note songs
TABLE 2. The use of 3-note songs by male Mountain Chickadees in various situations, compared to all
other song types. See Table I for an explanation of the format.
Individual males
All males Preferred song type
Situation n Preferred song“ z-value p 3-note Other None
Nest searching/building stage 5 3-note +5.71 <0.01 3 2 0
Egg-laying stage 6 -0.76 0.45 1 3 2
Incubation stage 6 Other -5.55 <0.01 0 3 3
Nestling stage 4 + 1.55 0.12 1 1 2
Near nest 6 Other -4.82 <0.01 0 4 2
Mate present 7 + 1.48 0.14 3 2 2
Undisturbed singing 7 3-note + 10.34 <0.01 5 0 2
Male-male interaction 6 +0.59 0.56 0 5
1
^Indicates that 3-note songs were u.sed significantly more frequently (3-note) or less frequently (Other)than expected in that situation. A blank indicates
no significant deviation from expected frequencies.
—
372 THE WILSON BULLETIN • Vol. Ill, No. 3, September 1999
TABLE 3. The use of common 3-note songs by male Mountain Chickadees compared to the use ofdescend-
ing 3-note songs in various situations. See Table 1 for an explanation of the format.
Individual males
Preferred song type
All males Descend-
- Common ing
Situation n Preferred song“ z-value p 3-note 3-note None
Nest searching/building stage 4 Common +8.73 <0.01 3 1 0
EgR-laying stage 6 Common +8.36 <0.01 3 2 1
Incubation stage 5 Descending -10.73 <0.01 2 3 0
Nestling stage 4 Descending -5.65 <0.01 1 2 1
Near nest 6 Descending -4.35 <0.01 3 2 1
Mate present 7 Common -6.56 <0.01 5 1 1
Undisturbed singing 4 +0.94 0.35 2 1 1
Male-male interaction 5 Descending -6.72 <0.01 0 3 2
^Indicates the 3-note song type that was used significantly more frequently than expected in that situation. A blank indicates no significant deviation
from expected frequencies.
during this situation whereas none used com- the song length analyses should be revealed
mon 3-note songs preferentially. in the song pitch analyses.
Different song types had significant asso-
DISCUSSION ciations with different breeding stages. How-
—
Individual song repertoires. Excluding in- ever, there was also much individual variation
frequent song types, males had individual rep- in all stages, with different males using dif-
ertoires of 4-7 song types. Hill and Lein ferent songs preferentially during the same
(1989) estimated a slightly smaller repertoire breeding stage. This suggests that although the
size of 3-5 song types. However, they sam- z-values were significant statistically, the re-
pled songs less intensively and may not have sults may not be meaningful biologically. Dif-
recorded enough songs to obtain complete ferent song types are probably not signaling
messages about the breeding stage of the sing-
song repertoires for all individuals.
Other researchers imply that the most com- er. Instead, different breeding stages may be
mon song type of Mountain Chickadees is a associated with other situations that are more
3-note song with all notes of the same pitch relevant biologically to the messages of the
(Gaddis 1985, Hailman 1989, Hill and Lein song type.
1989). In contrast, we found that males in our The number of notes in songs of Mountain
We Chickadees was associated significantly with
study rarely sang songs of this type. are
unable to explain this difference, but it may location relative to the singer’s nest. All in-
support Gaddis’ (1985) suggestion of geo- dividuals showing significant preferences ei-
graphical variation in Mountain Chickadee ther used more 2-note songs near the nest than
away from or more 3-notes away from the
it,
songs.
Use of .song types in different situations. nest than near it. Some other studies on song-
Our analyses of song length grouped different birds also have found that males sang different
song types with the same numbers of notes song types depending on their territorial lo-
into a single category, possibly obscuring cation (e.g., Lein 1978, Weary et al. 1994).
some patterns in the use of different song Although pitch of the last note in 3-note songs
types. However, because almost all 2-note was associated with location relative to the
songs recorded were common 2-note songs, nest, this association is weak because of the
the results from analyses of all 2-note songs large degree of individual variation.
would be almost identical to results using only In Mountain Chickadees, the tendency to
common 2-note songs. Almost all 3-note sing 2-note songs near the nest and 3-note
songs recorded were either common or de- songs away from the nest may be influenced
scending 3-note songs. Any differences be- by factors other than just the singer’s location.
tween these song types that were obscured in Males were more likely to engage in non-ag-
—
Wiehe am! Lein • SONG TYPES OF MOUNTAIN CHICKADEES 373
gressive activities while singing near the nest could convey more aggressive messages than
than when singing away from the nest, sug- 2-note songs.
gesting that location relative to the nest and Male-male interactions in Mountain Chick-
male behavior were related. Although note adees were associated with changes in pitch
number may communicate some information of notes in the song. Because most males were
about the singer’s location, these factors may more likely to sing common 3-note songs
be related only indirectly and the association when apparently unprovoked by another bird’s
between male behavior and note number may activities than during interactions with rival
be more important biologically. males, this song type may function in spon-
Different song types were associated with taneous advertisement of the territory. De-
the presence or absence of the singer’s mate. scending 3-note songs were associated with
Other researchers (e.g., Temrin 1986, Staicer male-male interactions and it is probable that
1989) have claimed that song types used pref- lowering the pitch of the last note in 3-note
erentially in the presence of females have a songs may convey some message to the rival.
greater intersexual function. One methodolog- Other researchers have suggested that song
ical problem in our study is that a female may types associated with male-male interactions
have been recorded as absent when she actu- probably convey more aggressive messages
ally was nearby in the nest hole, but not vis- than do other song types (e.g.. Nelson and
ible to the observer. Two-note songs and de- Croner 1991). Interactions between males are
scending 3-note songs, which were positively situations of high levels of agonistic stimula-
associated with the absence of the female, tion for Mountain Chickadees and so they
were also positively associated with the nest may be more likely to use songs that convey
site. Furthermore, in most cases singers did stronger aggressive tendencies at this time.
not seem to be directing song specifically at Thus, descending 3-note songs may convey
females. Males sometimes sang low-volume, more aggressive messages than common 3-
note songs.
“quiet” songs, usually of 1 or 2 notes, when
Comparison to closely-related species
approaching nests to feed incubating mates. .
Although such songs may be directed specif- Our findings suggest that the function of in-
ically at females, we never observed normal dividual repertoires in Mountain Chickadees
volume songs used in this manner. Therefore, is similar to that of other North American
we are hesitant, without further experimental chickadees and titmice, with different song
study, to suggest that common 3-note songs types used in different situations and appear-
ing to have different communicative func-
have a greater intersexual function than do 2-
note songs and descending 3-note songs. tions. Three species of North American tit-
mice have certain song types that are used
The behavior of singing males was associ-
predominantly in male-male interactions
ated with the number of notes in the song, but
(Gaddis 1983, Schroeder and Wiley 1983,
not with pitch. Two-note songs were positive-
Johnson 1987). These are probably similar in
ly associated with singing while engaged in
function to the descending 3-note song of the
non-aggressive activity and 3-note songs were
Mountain Chickadee, which is also used in
positively associated with undisturbed sing- male-male interactions. The Bridled Titmouse
ing. Although not all males had individual re- (Baeolophus wollweheri) has one song type
sults that were significant, all males showed used predominantly in spontaneous advertise-
this trend. ment of territory (Gaddis 1983). and we found
We
suggest that 3-note songs signal a high- that the common 3-note song of the Mountain
er motivation level of the singer to sing than Chickadee is used predominantly in undis-
do 2-note songs. If so, 3-note songs might in- turbed singing. Schroeder and Wiley (1983)
dicate that the singer is more willing to en- suggested that different song types ofthe Tuft-
gage in some of the agonistic actions associ- ed Titmouse (B. bicolor) convey different lev-
ated with singing in Mountain Chickadees, els of aggression by the singer. This corre-
such as countersinging bouts or interacting sponds to our suggestion that, in Mountain
with other males at the edge of the territory Chickadees, descending 3-note songs, com-
to confirm boundaries. Thus, 3-note songs mon 3-note songs, and 2-note songs indicate
374 THE WILSON BULLETIN • Vol. Ill, No. 3, September 1999
high, intermediate, and low levels of aggres- ation of territorial advertisement. In both spe-
sion, respectively. cies, pitch seems to be lowered during more
There are also some differences in the man- aggressive situations. Morton (1977) suggest-
ner in which titmice and Mountain Chicka- ed that calls of low pitch indicate higher ag-
dees use songs. For instance, the Bridled Tit- gressiveness by the signaler than do calls of
mouse has a song type used predominantly in higher pitch. This idea seems to be applicable
long-distance countersinging (Gaddis 1983). to song in Mountain Chickadees and Black-
We did not find any song type in Mountain capped chickadees.
Chickadees that was used in this manner, al- ACKNOWLEDGMENTS
though it is possible that some songs that we
categorized as “undisturbed” singing may S. R. M. Shima provided able assistance in collec-
have actually been in response to far away tion of the data. R Rodriguez de la Vega, M. R. Evans,
song that was inaudible to the observer. John- J. Bolstad, J. Goddard, and K. Olson also assisted with
son (1987) noted that the Plain Titmouse field work. We thank G. Chilton for his help and ad-
vice during various stages of the project. The staff at
{Baeolophus inornatus) was more likely to
the Barrier Lake site of the University of Calgary’s
use some song types in situations related to Kananaskis Field Stations provided support and ac-
nesting activities. Although 2-note songs were commodation during the field season. R. M. R. Bar-
associated with close proximity to the nest, clay, A. P. Russell, P. A.squith, and J. P. Hailman gave
there was no indication that Mountain Chick- constructive comments on earlier drafts of the manu-
adees were using these songs in any way that script. This research was supported by a graduate
scholarship from Ellis Bird Farm Limited and research
was related specifically to nesting activity. assistantships from the University ofCalgary to MOW,
Carolina Chickadees (Poecile carolinensis) and a research grant from the Natural Sciences and
have one song type associated with counter- Engineering Research Council of Canada to MRL.
singing that is thought to be a more aggressive
LITERATURE CITED
song type (Smith 1972). This song type could
be similar in function to descending 3-note American Ornithologists’ Union. 1997. Forty-first
songs given by Mountain Chickadees during supplement to the American Ornithologists’
male—male interactions. However, Smith Union Check-list of North American Birds. Auk
(1972) also observed that Carolina Chicka- 1 14:542-552.
Baker, M. C., T H. Bjerke, H. Lampe, and Y. Esp-
dees were more likely to use this aggressive
MARK. 1986. Sexual response of female Great Tits
song type while patrolling territorial bound- to variation in size of males' song repertoires. Am.
aries whereas we did not note any strong as- Nat. 128:491-498.
sociation between descending 3-note songs Bijnens, L. and a. a. Dhondt. 1984. Vocalizations in
and territorial boundaries. a Belgian Blue Tit, Pants c. caeruleus, popula-
Pitch may be an important cue in coding tion. Le Gerfaut 74:243-269.
Cochran, W. G. 1971. Some methods for strengthen-
information in the songs of both Mountain
and Black-capped chickadees, but the two ing the common x’ test. Pp. 132—156 in Readings
in statistics for the behavioral scientist (J. A. Ste-
species differ in how they vary the pitch of ger, Ed.). Holt, Rinehart, and Winston, New York.
their songs. Unlike Black-capped Chickadees, Dahlsten, D. L. and W. A. Copper. 1979. The use of
which shift the entire song downward in pitch. nesting boxes to study the biology of the Moun-
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