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Current Research Projects

Recent & Current Graduate students

Current papers

Recent publications



Broadly stated, the main research interests in this lab. concern the characterization and interpretation of patterns of behavioural (mainly song), morphological and genetic variation, among individuals, among populations or among species. We work primarily on passerine birds, and recent or current studies include: covariation in morphological, allozyme, mtDNA and song characteristics in the South American sparrow Zonotrichia capensis, ontogeny and discrimination of vocal dialects in Zonotrichia capensis, evaluation of the Acoustic Adaptation Hypothesis in the explanation of bird song-structure, evolutionary convergence among south American seedeating birds, and an ecomorphological study of the Neotropical furnariid radiation.

Recent Graduate Theses

Ph. D.
1990 Tubaro, P.L. Causal and functional aspects of patterns of variation in the song of Zonotrichia capensis.

1991 Lougheed, S.C. Covariation of song, morphological & allozyme frequency characters in the Rufous-collared sparrow, Zonotrichia capensis.

1998  Timothy Brown. Experimental analysis of  Acoustic Adaptation  in bird song.

1991 Lozano, G.A. Intrasexual competition and delayed plumage maturation in female Tree Swallows, Tachycineta bicolor.

Current Graduate Students

Ph. D.

Fernando Larrea. Vocal variation in tropical populations of Zonotrichia capensis.

Ha-Cheol Sung.  Aspects of variation in the song of the Savannah Sparrow, Pesserculus sandwichensis.

Current Papers

Brown, T.J. and P. Handford.   Acoustically adapted signals can be reliably ranged. Condor. (in review)

Abstract.  In passerines, the ability of listeners to range the distance of a conspecific signaler, by assessing the level of degradation contained in a received song, is well established.  This ability to range a signaler requires that the song degrade both increasingly and predictably with increasing transmission distance.  It is reasonable to expect acoustic degradation in closed habitats to be consistent across time, and thus predictable.  Degradation in open habitats, where atmospheric heterogeneities change from moment to moment, is likely to be variable, which in turn makes ranging a difficult proposition.  To investigate whether signals degrade increasingly and predictably with distance, we transmitted natural signals of contrasting structure [trilled song of the Swamp Sparrow (Melospiza georgiana), whistled song of the White-throated Sparrow (Zonotrichia albicollis)] through open grasslands and mature forests.  The received (degraded) signals were compared to the transmitted (non-degraded) version, and a measure of transmission quality, and the variability about that quality, were obtained.

 In open habitats, results reveal that only the trilled Swamp Sparrow song degraded increasingly and predictably with distance;  in closed habitats, only the whistled White-throated Sparrow song degraded increasingly and predictably with distance.  Thus, the trill- and whistle-structured songs degrade increasingly and predictably with distance only in open and closed habitats, respectively.  The significance of these results with respect to ranging, and the closely related topics of signaler identity and the acoustic adaptation hypothesis are discussed.

Kopuchian, C., D. Lijtmaer, P. Tubaro and P. Handford.  2004.  Temporal stability and change in a microgeographic pattern of song variation in the Rufous-collared sparrow.  Animal Behaviour  (in press;  accepted 28 August 2003).

Abstract.     We studied the microgeographic pattern of song variation in the Rufous-collared Sparrow (Zonotrichia capensis) in breeding seasons 1987 and 2000, along a transect of 7 km covering open and closed habitats. We measured 14 quantitative variables of song over a total of 390 individuals and found consistent differences between habitats along the study period. In particular, the song of closed habitat had trills with fewer notes, longer trill intervals, and lower acoustic frequencies than the open habitat ones. This pattern of variation is better described as a song cline that correlates with the environmental gradient. Although this cline was stable in location and shape, it also showed several changes between seasons. The songs of 1987 had trills with shorter trill intervals and both higher minimum and emphasized frequencies than those recorded during 2000. Thus, this study is the first to directly document song changes in a Z. capensis population. This change, however, did not correlate with any obvious change in habitat features during the study period.

Brown, T.J. &  P. Handford.  2003   WHY BIRDS SING AT DAWN: THE ROLE OF CONSISTENT SONG TRANSMISSION. Ibis 145: 120-129 (2003)

This work was featured on Quirks & Quarks, 28 June 2003.
Summary:  The dawn chorus is a widely observed phenomenon.  One of the common, but inadequately studied, explanations for the occurrence of the dawn chorus is based on the rationale that atmospheric turbulence, which impairs acoustic communication, is minimal at dawn relative to other times of day, and thus singing at dawn, in some way, maximizes signal performance.  To investigate what possible acoustic benefit is gained through singing at dawn, we transmitted Swamp Sparrow Melospiza georgiana and White-throated Sparrow Zonotrichia albicollis song through open grassland and closed forest both at dawn and midday.  The transmitted songs were re-recorded at four distances between 25-100 m.  Results show that mean overall absolute transmission quality of the signals at dawn was not significantly better than it was at midday.  However, the signal transmission quality at dawn was significantly more consistent than it was at midday.  Also, in general, signal transmission quality decreased with increasing distance.  Variability in the transmission quality increased with distance for the White-throated Sparrow song, but not for the Swamp Sparrow song.  Consistency in signal transmission quality is a factor that, arguably, is crucial for the identity function of song.  This study strongly supports the acoustic transmission hypothesis as an explanation for the existence of the dawn chorus while the demonstration of variability as a key factor in singing at dawn is novel.

Chilton, G.,  M. O. Wiebe and P. Handford  2002  LARGE SCALE GEOGRAPHIC VARIATION IN SONGS OF GAMBELíS WHITE-CROWNED SPARROWS. Condor  104:  378-386.

Abstract.  An earlier study failed to find dialectal variation in the songs of male Gambelís White-crowned Sparrows, Zonotrichia leucophrys gambelii in Alaska.  We recorded songs of males at five localities over a much greater portion of the subspeciesí range, spanning 2250 km east to west, and 1650 km north to south.  On this scale, distinct geographical variants are evident, based on the songís terminal phrase and the fine details of other phrases.  In White-crowned Sparrows, the extent of dialect groups is apparently positively correlated with the distance migrated by the subspecies; a demographic variable such as survivorship or natal philopatry likely result in this link.

M.C. Kalcounis, T. J. Brown and P.T. Handford.  2002  ECHOLOCATION CALL CHARACTERISTICS AND ACTIVITY OF BATS IN BIOMES OF NORTHWESTERN ARGENTINA .  Mastozoologia Neotropical.  (in press).

Abstract.  We examined echolocation call characteristics and activity of bats in 4 biomes of northwestern Argentina during August 1997 by monitoring echolocation calls.  Our aims were to evaluate the level of bat activity among five different biomes in northwestern Argentina and to investigate if echolocation signal structure characteristics were associated with biome type in a manner coincident with the general predictions. We sampled bat activity in sites representing puna, chaco, monte desert, selva basale and a riparian site.  No bats were recorded in the puna, while of the four remaining biomes, the least to the most active were; monte, selva, chaco and transitional chaco.  Echolocation calls did not differ significantly among the monte, chaco or selva biomes, while the transitional chaco-calls were significantly different, being more intense (rapid) and of a higher frequency.  Modal frequency of call search phases revealed selva-calls to be of a higher modal frequency than calls from other biomes.  Our study illustrates that the lesser complex biomes tend to be less active.  Modal frequency of call search phases was the single character that did differed predictably among the biomes.

Lougheed, S.C., J. Freedland, P. Handford and P. Boag. 2000. Convergence and Paraphyly in a Neotropical Passerine Genus.  Molecular Evolution & Phylogenetics. 17: 367-378.

 Abstract.-- We investigated the evolutionary history of 12 species within a single genus of neotropical passerine (Poospiza ) using sequence from the 16S rRNA and cytochrome B mitochondrial genes. Evolutionary tree topologies derived using different algorithms and different subsets of the sequence data were similar, although basal relationships among clades within the ingroup taxa remain unresolved. The phylogenetic hypothesis derived from molecular data was discordant with that based on plumage, morphology and behavior. Thus, these characters probably cannot be assumed to be either neutral (taxonomically-useful) or phylogenetically-constrained, at least at this taxonomic level. Pair-wise divergence between Poospiza species was high compared to that of published estimates for temperate avian congeners (range for cytochrome B: 5% to 17.7%; for 16S rDNA 0.6% to 3.8%). Cytochrome B sequence divergence (5.9%) between two P. torquata individuals derived from disjunct ranges in Argentina and Bolivia approached some of the upper values for temperate intrageneric comparisons and exceeded even some interspecific comparisons within the present study. These results are consonant with a number of recently published studies that suggest that neotropical taxa contain much deeper phylogenetic divisions than their temperate (predominantly nearctic) counterparts. Key words.-- birds, mtDNA, differentiation, phylogeny, Poospiza, neotropical, convergence.

Brown, T.J. and P. Handford. 2000. Sound design for vocalizations: quality in the woods, consistency in the fields.Condor 102:  81-92.

 Abstract. The acoustic adaptation hypothesis (AAH) predicts that vocalizations intended for unambiguous long range communication should possess amplitude modulation (AM) characteristics such that the temporal patterning of amplitude degrades (due to reverberation and / or atmospheric turbulence) less than alternative patterns during transmission through native habitat. The specific predictions are that open habitat signals should be structured as rapid AM trills, while closed habitat signals should be structured as low rate AM tonal whistles. To investigate the benefit of trill- and whistle-structured signals in open and closed habitats respectively, a high and low carrier frequency set of four synthetic signals which ranged from rapid AM trills to low rate AM whistles were transmitted 3 hours after sunrise through 5 different habitat types ranging from closed mature forest to open grassland. The received (degraded) signals were compared to the transmitted (non-degraded) version, and a measure of transmission quality obtained.

 Results indicate that, on average, whistles degrade less than trills in all habitat types. However, trills benefit in open habitats through their tendency to be received with a more consistent quality than do whistles. Such differences in transmission consistency among AM patterns are not found in closed habitats. Although they do not degrade less on average, lower frequency signals are received with a more consistent quality than are higher frequency signals, of the same AM structure, in both open and closed habitats. The results, and particularly the importance of signal transmission consistency, are discussed in relation to species identifiability and signal ranging.

Handford, P. 1999. Inferring the Past. paper invited by Ciencia Hoy, an Argentine journal of the sciences.   vol 9 No. 52.

Véase el articulo original.

Recent Publications From The Lab.

Tubaro, P.L., P. T. Handford and E.T. Segura 1997 Song learning in the Rufous-collared sparrow (Zonotrichia capensis). Hornero 14: 17-23.

Brown, T.J. and P.Handford 1996 Acoustic signal amplitude patterns: a computer simulation investigation of the Acoustic Adaptation Hypothesis. Condor 98(3): 608-623.

Lougheed, S.C., P. Handford and A.J. Baker 1993 Mitochondrial DNA hyperdiversity, vocal dialects and subspecies in the Rufous-collared sparrow, Zonotrichia capensis. Condor 95:889-895.

Lougheed, S.C.& P. Handford 1993 Covariation of song, morphological and allozyme frequency characters on populations of the Rufous-collared sparrow, Zonotrichia capensis. Auk 110:179-188.

Tubaro, P., E. Segura and P. Handford. 1993 Geographic variation in the song of the Rufous-collared sparrow (Zonotrichia capensis.) in eastern Argentina. Condor 95:588-595.

Yezerinac, S.M., Lougheed, S.C. and P. Handford. 1992a. Measurement error and morphometric studies: statistical power and the effect of observer experience. Systematic Biology 41:471-482.

Yezerinac, S.M., Lougheed, S.C. and P. Handford. 1992b. Heterozygosity and morphological variability revisited. Evolution. 46:1959-1964.

Lougheed, S.C. and P. Handford. 1992. Vocal dialects and the structure of geographic variation in morphological and allozymic characters in the Rufous-collared sparrow, Zonotrichia capensis.Evolution 46:1443-1456.

Handford, P. & Lougheed, S.C. 1991 Variation in duration and frequency characters in the song of the Rufous-collared sparrow, Zonotrichia capensis, with respect to habitat, trill dialects and body size. Condor 93: 644-658.

Austen, M.J.W and P. Handford 1991 Variation in the songs of breeding Gambel's White-crowned sparrows near Churchill, Manitoba. Condor 93:147-152.

Handford, P. 1988. Trill rate dialects in the Rufous-collaredsparrow, Zonotrichia capensis,in northwestern Argentina. Can. J. Zool. 66:2658-2670. 

Abstract of:

Brown, T.J. and P.Handford 1996
Acoustic signal amplitude patterns: a computer simulation investigation of the Acoustic Adaptation Hypothesis. Condor 98(3): 608-623.

The acoustic adaptation hypothesis (AAH) predicts that vocalizations intended for unambiguous long range communication should possess amplitude modulation (AM) characteristics such that the temporal patterning of amplitude is minimally degraded (due to atmospheric turbulence and reverberation) during transmission through native habitat. Specifically, signals should possess rapid AM (trills) in open habitats and low rate AM (whistles) in closed habitats.

 To determine which of these amplitude patterns incurs less degradation from its two main components, reverberation and irregular amplitude fluctuations (IAFs), we constructed two synthetic 'source' signals, a rapid AM 'trill' and a low rate AM 'whistle', from pure tone frequency sweeps. We applied the degradation components independently, thus avoiding their complex interactions typical of field recordings. Signals were degraded by various echo treatments (modelling closed habitat reverberation) or by various amplitude decrease treatments (modelling open habitat IAFs).

 Results revealed that the difference in performance between signal types lies not so much in their average transmission quality, as in the variability of that quality. In closed habitats, whistled signals transmit with more consistent quality than trilled signals over biologically realistic echo delays. In open habitats, trilled signals transmit with far lower variability of quality than do whistled signals. The inherent redundancy of trills transmits information more effectively than whistles in open habitats. Our results show strong support for the AAH predictions regarding what type of signal structure is best suited for open or closed habitats. However, this support is based on variability in performance of signal types in different habitats rather than average transmission quality.

 Key Words: Acoustic Adaptation Hypothesis; computer simulation; amplitude modulation; reverberation; irregular amplitude fluctuations; open habitats; closed habitats.

Abstract of:

Lougheed, S.C., P. Handford and A.J. Baker  1993
Mitochondrial DNA hyperdiversity, vocal dialects and subspecies
in the Rufous-collared sparrow, (Zonotrichia capensis).
Condor 95:  889-895.

The Rufous-collared Sparrow, Zonotrichia capensis,  is widely distributed in neotropical America and shows extensive variation in its learned song.  In northwestern Argentina it exhibits song dialects which map closely onto the distribution of natural vegetation assemblages.  To date, there is no evidence of a correlation between genetic (allozyme) variation and dialects.  However, recent genetic structuring produced through philopatry and assortative mating by dialect, is difficult to demonstrate statistically with such protein-encoding nuclear genes. Therefore, we assayed variation in more rapidly evolving mitochondrial DNA along a 50 km transect, which spans three dialect boundaries between four adjacent habitat-types (from ~1800 m. to ~3000 m.), using restriction fragment length polymorphism analysis.  This revealed exceptional diversity (41 clones from 42 individuals), a level comparable with DNA-fingerprinting, and higher than reported in any passerine over such a small area to date.  The degree of nucleotide divergence between the two main clusters of mtDNA haplotypes implies a separation time in excess of one million years.  The mtDNA variability is not related to song dialects; rather it is interpreted as a reflection of secondary introgression between two well-differentiated subspecies whose ranges abut in this region.

Key Words:  mtDNA, hypervariability, vocal dialects, introgression, Rufous-collared Sparrow, Zonotrichia capensis, Argentina

Abstract of:

Lougheed, S.C. & P. Handford  1993
Covariation of song, morphological and allozyme frequency characters in
populations of the Rufous-collared sparrow,  Zonotrichia capensis .
Auk  110:  179-188.

We collected 474 specimens of male Rufous-collared Sparrows (Zonotrichia capensis)  from 24 sites in northwestern Argentina.  Four samples from each of six different habitats: lowland chaco thornscrub, transition forest, montane woodland, montane grassland, Monte desert scrub, and puna high altitude scrub.  Puna birds (Z. c. pulacayensis) were differentiated both genetically and morphologically from all other birds in the sample (Z. c. hypoleuca). However, the steepness and location of the clines for these two character types were substantially different.  An abrupt cline in PGM-1 allozyme frequencies was apparent in the extreme northwest of our study area, while clines in morphological features (primarily body size) were gradual and extended much further southward.  Among nonpuna samples (20 sites;  Z. c. hypoleuca), patterns of intersite differentiation in morphological and allozyme characters were unrelated.  Partial Mantel's tests showed that, among these samples, both degree of difference in habitat structure and linear geographic distance are important correlates of among-site morphological differentiation.  Similar tests demonstrated that neither of these two environmental factors is related statistically to genetic differentiation among populations.

Abstract of:

Yezerinac, S.M., S.C. Lougheed and P. Handford.  1992a
Measurement error and morphometric studies:  statistical power and the effect of observer experience.
Systematic Biology  41:  471-482.

We estimated measurement error (ME) seperately for fifteen skeletal characters of seven passerine birds. After making three measurements of each character the total sample variance of a character was partitioned into among- and within?individual components of variation. Within-individual variation is attributable to ME and ranged from < 1 % to > 80 %.  %ME was inversely related to the size of a character, among-individual variability of a character and experience of the measurer. Other sources of ME included the characterís flexibility and the definition of character landmarks. Observer experience reduced ME, however the effect was only substantial after more specimens were measured than are used in many morphometric studies. The magnitude of detectable effect size for parametric statistical tests of between group differences was examined in relation to the level of ME and the sample size of groups being compared.  ME increased the chances of making Type II errors.  Type II errors can be reduced either by averaging two or more repeated measurements of the same individual, thereby reducing ME, or by increasing the sample size. We show how averaging repeated measurements changes the minimum detectable effect size between groups when ME and sample size vary. The pattern of character-specific measurement error is consistent across passerine species: both good and poor characters for future morphometric studies are identified. [measurement error; morphometrics; type II error; passerine(s); model II ANOVA; statistical power]

Abstract of:

Lougheed, S.C. and P. Handford.  1992.
Vocal dialects and the structure of geographic variation in
morphological and allozymic characters in the Rufous-collared sparrow, Zonotrichia capensis.
Evolution  46:  1443-1456.

The geographical patterns of variation shown at 20 allozyme and non-enzymatic protein-coding loci, in 8 external, and in 12 skeletal morphological characters in the rufous-collared sparrow,  Zonotrichia capensis, were analysed in order to test the local (genetic) adaptation hypothesis regarding the origin and maintenance of vocal dialects in birds.  Approximately 20 males were collected from each of four sites within each of six different dialect zones.  There was significant variability in both external and skeletal morphology among all 24 sites and among dialect groups.   Average Wright's corrected fixation coefficient (FST) was 0.118, indicating significant genetic differentiation among all sites, regardless of dialect.  Hierarchical F statistics indicated that only 50 % of among site variability was due to a dialect effect.

Puna dialect sites were highly differentiated from all other sites with respect to both morphology (external and skeletal measures) and allozyme frequencies.  Heterogeneity at the PGM-1 locus among puna scrub sites was the major cause of the high average FST across all sites, and within the puna scrub dialect.  Average genetic differentiation among non-puna sites (FST  = 0.018) was similar to differentiation among sites within each of the five non-puna dialect groups (mean FST  = 0.0132 ± 0.0069).  Hierarchical F statistics indicated that none of the among-site differentiation in this subset of samples was due to a dialect effect.
These observations are not consistent with the local adaptation hypothesis.  All significant genetic heterogeneity occurred among sites in mountainous habitats, and we suggest that topography and patchiness of habitat may have been major factors involved in population differentiation, rather than vocal dialects.

Key words. -- rufous-collared sparrows,  Zonotrichia capensis ,  vocal dialects, population structure, variation, allozymes, morphology.

Abstract of:

Handford, P. & S.C. Lougheed  1991
Variation in duration and frequency characters in the song of the Rufous-collared sparrow,
Zonotrichia capensis,  with respect to habitat, trill dialects and body size.
Condor 93:  644-658.

We present data on variation in frequency and duration characters of the advertising song of Zonotrichia capensis, the Rufous-collared sparrow, and information on the qualitative structure of the introductory "theme".  These data are analyzed with respect to their relationships with altitude, habitat-type, body size, syrinx size and the dialect variation shown by the terminal trill.

Principal components analysis shows that the major axis of variation (PC1) in the frequency and duration variables is one primarily of increasing frequency and bandwidth of the trill (mainly due to increasing maximum trill frequency),  increasing frequency of the theme,  and of increasing song length, mainly contributed by theme length;  increasing values on PC2 correspond to an increasing theme bandwidth and maximum theme frequency, with decreasing theme length and increasing trill length.

PC1 scores from this analysis are negatively correlated with altitude over the whole sample.  Higher-altitude habitats are usually structurally open;  lower-altitude habitats usually mixed or closed.  Songs from the nine categories of original, natural vegetation differ significantly in their PC1 scores, while contemporary vegetation structure has no significant effect:  songs from the open-country habitats, desert, puna and grassland, are shorter, have lower frequency and narrower bandwidth than all woodland, thornscrub and forest songs.

With the exception of the very slow-trilled songs from the Monte desert dialect, there is a positive relationship between trill interval and PC1 score :  slower-trilled songs (longer trill interval; lower trill rate) are longer, of higher frequency and broader bandwidth.  The slow-trill Monte dialect songs are anomalous in having PC1 characteristics like the fastest-trilled dialect songs (puna and grassland).

  There is a significant negative relationship between body size and PC1, though it is non-linear:  birds from all habitats but puna are very similar in having smaller body-size.  Syrinx size is not correlated either with measures of body-size or with habitat.  It is concluded that most variation in song modal frequency and bandwidth is due to learning processes, rather than to size constraints of the body or organs.

KEY WORDS:  Zonotrichia capensis ;  Rufous-collared sparrow ;  dialects;  song variation;  ecological correlates;  body size;  morphological constraints.

Abstract of:

Austen, M.J.W and P. Handford  1991
Variation in the songs of breeding Gambel's White-crowned sparrows near Churchill, Manitoba.
Condor 93:  147-152.

Song variation was studied in Gambel's White-crowned Sparrows, (Zonotrichia  leucophrys  gambelii), breeding in tundra and boreal forest habitats near Churchill, Manitoba.  No significant differences were found among habitats in song characteristics of Z. l. gambelii.  Songs of Churchillbirds had the same sequence of elements (i.e. whistle, warble, buzz, and trill) as Alaskan populations, with some variations in element form.  The absence of dialects in migratory populations of White-crowned Sparrows supports predictions of the Ranging Hypothesis.

 Key Words: Song; song variation; White-crowned Sparrow; Zonotrichia leucophrys.

Abstract of:

Handford, P.  1988
Trill rate dialects in the Rufous-collared sparrow, Zonotrichia capensis, in northwestern Argentina.
Can. J. Zool.  66:  2658-2670.

Geographical variationin the trill rate of Zonotrichia capensis was assessed in a sample of about 2300 individuals from nearly 600 sites distributed throughout northwestern Argentina, from 22 to 34°S.  The variation was partitioned among the following site characteristics:  original (natural) vegetation, contemporary vegetation structure, latitude, longitude and altitude.  About 45% of the variation was attributable to the original vegetation (p<0.0001):  the other site characteristics explained a further 4%.  Thus the geographical distribution of trill rate closely paralleled that of the natural vegetation, even where this vegetation has been long (80-100 years) replaced by various forms of agriculture.  These results were interpreted as the consequence of vocal learning influenced by the vocalizations of dominant elements in the local avifauna of each habitat, together with factors affecting the unambiguous propagation of acoustic signals through different kinds of vegetation.

Paul Handford <>

Last revised: 03/10