Biodiversity Data Journal :
Research Article
|
Corresponding author: Shari Limbo Guerra (slguerra@up.edu.ph), Juan Carlos T. Gonzalez (jtgonzalez@up.edu.ph), Emmanuel Francisco Rafael (efrafael@seaza.asia)
Academic editor: Yasen Mutafchiev
Received: 17 Nov 2018 | Accepted: 05 Nov 2019 | Published: 13 Nov 2019
© 2019 Shari Guerra, Juan Carlos Gonzalez, Emmanuel Francisco Rafael
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Guerra SL, Gonzalez JCT, Rafael EF (2019) Description and comparison of Philippine hornbill (Bucerotidae) vocalizations. Biodiversity Data Journal 7: e31723. https://doi.org/10.3897/BDJ.7.e31723
|
|
The role of vocalisation for the Philippine hornbills' ecology and speciation and their implication in understanding speciation is not well understood. We described and compared recorded calls of seven hornbill taxa in captivity namely Mindanao Wrinkled hornbill (Rhabdotorrhinus leucocephalus), Rufous-headed hornbill (Rhabdotorrhinus waldeni), Luzon Rufous hornbill (Buceros hydrocorax hydrocorax), Samar Rufous hornbill (Buceros hydrocorax semigaleatus), Mindanao Rufous hornbill (Buceros hydrocorax mindanensis), Mindanao Tarictic hornbill (Penelopides affinis), Samar Tarictic hornbill (Penelopides samarensis), Visayan Tarictic hornbill (Penelopides panini) and Luzon Tarictic hornbill (Penelopides manillae), as well as comparison with the non-native Papuan hornbill (Rhyticeros plicatus). Vocalisation analysis included call duration, minimum frequency, maximum frequency, bandwidth and peak frequency. For each species in the sample, the mean and standard deviation were used to calculate the Cohen’s d statistic by using an effect size calculator. Results showed that the effect size for minimum frequency was small for P. panini vs. P. samarensis and B. hydrocorax vs. B. h. mindanensis. However, bandwidth, duration, minimum frequency, maximum frequency and peak frequency have large effect sizes for the rest of the allopatric species pairs. Hornbills' conspicuous resonating calls are sufficiently quantifiable for bioacoustic analysis and may provide new insights for their taxonomic review.
Species limits, hornbills, vocalisation, bioacoustics
Hornbills (Bucerotidae) are a charismatic group of tropical birds, under the Order Bucerotiformes, recognised for their long decurved bill supported with a prominent casque. Some 60-64 species of Bucerotiformes are currently recognised worldwide, including two species of ground-hornbills within the family Bucorvidae. The majority of the species belong to the family Bucerotidae and which all share the unique trait of plastering the nest-cavity (
The resounding vocalisations of hornbills aids their communication interaction with conspecifics and sympatrics in dense forest habitats, defence, territory and threat (
Studies by
Study site and recording of vocalisations
Observations took place during the day and the advertisement calls were recorded on an opportunistic basis with a Sony PBR-330 parabolic reflector, Uniso UC-0163 hands-free microphone and Sony IC recorder ICD-BX140. During the recording of the calls, the microphone was approximately 8 to 10 metres away from the hornbill species in captivity. The male hornbills, used in the study, were inside the cages with the other hornbills of the same species. The majority of the vocal sampling was derived from captive hornbills due to the limitations of recording vocalisations of Philippine hornbills in the wild. For comparison, analysis was supplemented by recordings available from online databases.
Adult male captive hornbills in Avilon Zoo, Rodriguez, Rizal were used in this study (Fig.
Analysis
Each individual had six to ten replicates and the non-overlapping vocalisations with the lowest background noise were used for analysis. The editing and noise reduction tools were utilised in Audacity 2.1.3 to eliminate unnecessary noise. Recordings were digitised and analysed using waveforms and spectrograms generated by Raven Pro 1.2 software. The vocalisations were quantified following the criteria proposed by
For each individual in the sample, the individual average for each parameter was determined. Thereafter, the mean and standard deviation were used to calculate the effect size index (
Trait | Magnitude (Score) | ||||
Frequency of scoring | Minor (1) | Medium (2) | Major (3) | Exceptional (4) | |
Morphology (biometrics) | Strongest increase and strongest decrease only | Effect size: 0.2-2 | Effect size: 2-5 | Effect size: 5-10 | Effect size: >10 |
Acoustics | Strongest temporal and spectral character only | Effect size: 0.2-2 | Effect size: 2-5 | Effect size: 5-10 | Effect size: >10 |
Plumage and bare parts | Three strongest characters | A slightly different wash or suffusion to all parts of any area | Distinctly different tone/shade to all or part of a significant area of feathering | Contrastingly different hue/colour to all or part of a significant part of a significant area of feathering | Radically different colouration or pattern to most of plumage (striking contrast in colour, shade, shape) |
Geographical relationship | n/a | Broad hybrid zone | Narrow hybrid zone | Parapatry | n/a |
Vocalisations of hornbills were found to reveal information on the individual (
For this study, there were six individuals for P. affinis, five for P. manillae and four for P. panini and P. samarensis (Table
Summary of mean, standard deviation, number of individuals, pooled variance, Cohen’s d score and total score using a standard quantitative criteria (Tobias et al. 2010) for compared species of Penelopides sp.
Vocal Characters | Mean | SD | n | Mean | SD | n | Pooled variance | Cohen's d | Score | Total Score |
P. affinis | P. panini | |||||||||
Bandwidth | 4.6735 | 0.2377 | 6 | 5.5377 | 0.0907 | 4 | 0.1753 | 4.93 | 2 | 5 |
Duration | 0.1875 | 0.0148 | 6 | 0.1571 | 0.0091 | 4 | 0.01 | 2.63 | 2* | |
Minimum Frequency | 2.0346 | 0.2023 | 6 | 1.8686 | 0.071 | 4 | 0.1482 | 1.12 | 1 | |
Maximum Frequency | 6.7081 | 0.1495 | 6 | 7.4063 | 0.0841 | 4 | 0.1153 | 6.06 | 3** | |
Peak Frequency | 4.7272 | 0.1604 | 6 | 4.171 | 0.0811 | 4 | 0.1218 | 4.57 | 2 | |
P. affinis | P. manillae | |||||||||
Bandwidth | 4.6735 | 0.2377 | 6 | 5.1882 | 0.1053 | 5 | 0.1724 | 2.99 | 2 | 6 |
Duration | 0.1875 | 0.0148 | 6 | 0.1244 | 0.0046 | 5 | 0.01 | 6.1 | 3* | |
Minimum Frequency | 2.0346 | 0.2023 | 6 | 1.3492 | 0.0995 | 5 | 0.149 | 4.6 | 2 | |
Maximum Frequency | 6.7081 | 0.1495 | 6 | 6.5374 | 0.15 | 5 | 0.1354 | 1.26 | 1 | |
Peak Frequency | 4.7272 | 0.1604 | 6 | 3.2542 | 0.1704 | 5 | 0.1492 | 9.88 | 3** | |
P. affinis | P. samarensis | |||||||||
Bandwidth | 4.6735 | 0.2377 | 6 | 4.1438 | 0.0929 | 4 | 0.1756 | 3.02 | 2 | 5 |
Duration | 0.1875 | 0.0148 | 6 | 0.2562 | 0.0345 | 4 | 0.02 | 3.18 | 2* | |
Minimum Frequency | 2.0346 | 0.2023 | 6 | 1.8855 | 0.0792 | 4 | 0.1495 | 1 | 1 | |
Maximum Frequency | 6.7081 | 0.1495 | 6 | 6.0293 | 0.0456 | 4 | 0.1086 | 6.25 | 3 | |
Peak Frequency | 4.7272 | 0.1604 | 6 | 3.8559 | 0.0806 | 4 | 0.1217 | 7.16 | 3** | |
P. manillae | P. samarensis | |||||||||
Bandwidth | 5.1882 | 0.1053 | 5 | 4.1438 | 0.0929 | 4 | 0.0884 | 11.82 | 4** | 7 |
Duration | 0.1244 | 0.0046 | 5 | 0.2562 | 0.0345 | 4 | 0.02 | 6.55 | 3* | |
Minimum Frequency | 1.3492 | 0.0995 | 5 | 1.8855 | 0.0792 | 4 | 0.0806 | 6.66 | 3 | |
Maximum Frequency | 6.5374 | 0.15 | 5 | 6.0293 | 0.0456 | 4 | 0.1034 | 4.91 | 2 | |
Peak Frequency | 3.2542 | 0.1704 | 5 | 3.8559 | 0.0806 | 4 | 0.1227 | 4.9 | 2 | |
P. panini | P. samarensis | |||||||||
Bandwidth | 5.5377 | 0.0907 | 4 | 4.1438 | 0.0929 | 4 | 0.0795 | 17.53 | 4 | 6 |
Duration | 0.1571 | 0.0091 | 4 | 0.2562 | 0.0345 | 4 | 0.02 | 4.54 | 2* | |
Minimum Frequency | 1.8686 | 0.071 | 4 | 1.8855 | 0.0792 | 4 | 0.0651 | 0.26 | 1 | |
Maximum Frequency | 7.4063 | 0.0841 | 4 | 6.0293 | 0.0456 | 4 | 0.0586 | 23.51 | 4** | |
Peak Frequency | 4.171 | 0.0811 | 4 | 3.8559 | 0.0806 | 4 | 0.07 | 4.5 | 2 | |
P. manillae | P. panini | |||||||||
Bandwidth | 5.1882 | 0.1053 | 5 | 5.5377 | 0.0907 | 4 | 0.09 | 3.99 | 2 | 6 |
Duration | 0.1244 | 0.0046 | 5 | 0.1571 | 0.0091 | 4 | 0.01 | 5.39 | 3* | |
Minimum Frequency | 1.3492 | 0.0995 | 5 | 1.8686 | 0.071 | 4 | 0.08 | 6.66 | 3 | |
Maximum Frequency | 6.5374 | 0.15 | 5 | 7.4063 | 0.0841 | 4 | 0.11 | 7.82 | 3** | |
Peak Frequency | 3.2542 | 0.1704 | 5 | 4.171 | 0.0811 | 4 | 0.12 | 7.46 | 3 | |
*strongest temporal character | **strongest spectral character |
The effect sizes for P. affinis vs. P. panini were large for all vocal characteristics- bandwidth (4.93), duration (2.63), minimum frequency (1.12), maximum frequency (6.06) and peak frequency (4.57). A score of 5 was given to the species pair due to obtaining medium (2) and major (3) scores for the strongest temporal and strongest spectral characters, respectively.
On the other hand, P. affinis vs. P. manillae also generated a large effect size for bandwidth (2.99), duration (6.10), minimum frequency (4.60), maximum frequency (1.26) and peak frequency (9.88). The strongest temporal and strongest spectral character resulted in a score of 6. Thus, the large effect sizes amongst the species in Penelopides strongly demonstrated variation in vocalisation amongst the taxon.
The magnitude of the strongest temporal and strongest spectral characters were 2 and 3, respectively. In total, a score of 5 was given to P. affinis and P. samarensis due to obtaining large effect sizes for all vocal characteristics – bandwidth (3.02), duration (3.18), minimum frequency (1.00), maximum frequency (6.25) and peak frequency (7.16) acquired large effect sizes.
Between P. manillae vs. P. samarensis, the effect size was also large for all variables, earning a score of 7 – bandwidth (11.82), duration (6.55), minimum frequency (6.66), maximum frequency (4.91) and peak frequency (4.90). The major and exceptional values of duration and bandwidth resulted in a score of 7.
However, P. panini vs. P. samarensis had a small effect size on minimum frequency (0.26), but the other variables, bandwidth (17.53), duration (4.54), maximum frequency (23.51) and peak frequency (4.50), had large effect sizes. A score of 6 was given to the species pair upon acquiring medium and exceptional values.
Lastly, P. manillae vs. P. panini received a score of 6 because of having large effect sizes for bandwidth (3.99), duration (5.39), minimum frequency (6.66), maximum frequency (7.82) and peak frequency (7.46). Both of the greatest temporal and spectral characters gained major scores for the total cumulative score.
There were five individuals for R. leucocephalus, three for R. plicatus and one for R. waldeni Table
Summary of mean, standard deviation, number of individuals, pooled variance, Cohen’s d score and total score score using a standard quantitative criteria (Tobias et al. 2010) for compared species amongst Rhabdotorrhinus leucocephalus, Rhabdotorrhinus waldeni and Rhyticeros plicatus.
Vocal Characters | Mean | SD | n | Mean | SD | n | Pooled variance | Cohen's d | Score | Total Score |
R. leucocephalus | R. waldeni | |||||||||
Bandwidth | 3.8984 | 0.0901 | 5 | 4.2894 | 0.1198 | 1 | 0.0736 | 5.31 | 3** | 6 |
Duration | 0.2878 | 0.0151 | 5 | 0.2 | 0.0145 | 1 | 0.01 | 7.14 | 3* | |
Minimum Frequency | 0.7293 | 0.041 | 5 | 0.6288 | 0.0189 | 1 | 0.0335 | 3 | 2 | |
Maximum Frequency | 4.6244 | 0.1046 | 5 | 4.9182 | 0.1284 | 1 | 0.0854 | 3.44 | 2 | |
Peak Frequency | 2.5908 | 0.1454 | 5 | 2.0413 | 0.364 | 1 | 0.1187 | 4.63 | 2 | |
R. leucocephalus | R. plicatus | |||||||||
Bandwidth | 3.8984 | 0.0901 | 5 | 3.0039 | 0.1983 | 3 | 0.1179 | 7.59 | 4 | 7 |
Duration | 0.2878 | 0.0151 | 5 | 0.5875 | 0.0978 | 3 | 0.05 | 5.99 | 3* | |
Minimum Frequency | 0.7293 | 0.041 | 5 | 0.2261 | 0.0303 | 3 | 0.0327 | 15.38 | 4** | |
Maximum Frequency | 4.6244 | 0.1046 | 5 | 3.23 | 0.2017 | 3 | 0.1251 | 11.15 | 4 | |
Peak Frequency | 2.5908 | 0.1454 | 5 | 0.8506 | 0.1025 | 3 | 0.1149 | 15.15 | 4 | |
R. waldeni | R. plicatus | |||||||||
Bandwidth | 4.2894 | 0.1198 | 1 | 3.0039 | 0.1983 | 3 | 0.1402 | 9.17 | 3 | 7 |
Duration | 0.2 | 0.0145 | 1 | 0.5875 | 0.0978 | 3 | 0.07 | 5.6 | 3* | |
Minimum Frequency | 0.6288 | 0.0189 | 1 | 0.2261 | 0.0303 | 3 | 0.0214 | 18.78 | 4** | |
Maximum Frequency | 4.9182 | 0.1284 | 1 | 3.23 | 0.2017 | 3 | 0.1426 | 11.84 | 4 | |
Peak Frequency | 2.0413 | 0.364 | 1 | 0.8506 | 0.1025 | 3 | 0.0725 | 16.43 | 4 | |
*strongest temporal character | **strongest spectral character |
Summary of mean, standard deviation, number of individuals, pooled variance, Cohen’s d score and total score score using a standard quantitative criteria (Tobias et al. 2010) for compared subspecies of B. hydrocorax.
Vocal Characters | Mean | SD | n | Mean | SD | n | Pooled variance | Cohen's d | Score | Total Score |
B. h. hydrocorax | B. h. mindanensis | |||||||||
Bandwidth | 2.1809 | 0.0945 | 3 | 2.493 | 0.0624 | 7 | 0.0642 | 4.86 | 2 | 3 |
Duration | 0.292 | 0.0226 | 3 | 0.2713 | 0.0038 | 7 | 0.01 | 1.97 | 1* | |
Minimum Frequency | 0.5065 | 0.0159 | 3 | 0.5035 | 0.0093 | 7 | 0.0101 | 0.29 | 1 | |
Maximum Frequency | 2.6873 | 0.0894 | 3 | 2.9965 | 0.0621 | 7 | 0.0626 | 4.94 | 2 | |
Peak Frequency | 0.8234 | 0.0123 | 3 | 0.9223 | 0.0248 | 7 | 0.02 | 4.95 | 2** | |
B. h. hydrocorax | B. h. semigaleatus | |||||||||
Bandwidth | 2.1809 | 0.0945 | 3 | 4.6767 | 0.022 | 2 | 0.06 | 4.21 | 2 | 8 |
Duration | 0.292 | 0.0226 | 3 | 0.563 | 0.0434 | 2 | 0.02 | 11.23 | 4* | |
Minimum Frequency | 0.5065 | 0.0159 | 3 | 0.7911 | 0.023 | 2 | 0.01 | 13.02 | 4 | |
Maximum Frequency | 2.6873 | 0.0894 | 3 | 5.4678 | 0.0197 | 2 | 0.06 | 8.58 | 3 | |
Peak Frequency | 0.8234 | 0.0123 | 3 | 3.1199 | 0.3915 | 2 | 0.18 | 13.1 | 4** | |
B. h. hydrocorax | B. h. mindanensis | |||||||||
Bandwidth | 2.1809 | 0.0945 | 3 | 2.493 | 0.0624 | 7 | 0.0642 | 4.86 | 2 | 3 |
Duration | 0.292 | 0.0226 | 3 | 0.2713 | 0.0038 | 7 | 0.01 | 1.97 | 1* | |
Minimum Frequency | 0.5065 | 0.0159 | 3 | 0.5035 | 0.0093 | 7 | 0.0101 | 0.29 | 1 | |
Maximum Frequency | 2.6873 | 0.0894 | 3 | 2.9965 | 0.0621 | 7 | 0.0626 | 4.94 | 2 | |
Peak Frequency | 0.8234 | 0.0123 | 3 | 0.9223 | 0.0248 | 7 | 0.02 | 4.95 | 2** | |
*strongest temporal character | **strongest spectral character |
Between R. leucocephalus vs. R. waldeni, bandwidth (5.31), duration (7.14), minimum frequency (3.00), maximum frequency (3.44) and peak frequency (4.63) have large effect sizes. The strongest temporal and spectral characters attained a medium score which resulted in a total score of 6. As seen in Table
Phenotypic scores and molecular divergence (
Species/subspecies pair |
Phenotypic scores |
Total phenotypic score |
% molecular divergence |
||||
Biometrics |
Plumage and bare parts |
Vocalisation |
Geographical relationship |
||||
1 |
Penelopides affinis Penelopides manillae |
2 |
6 |
6 |
0 |
14 |
3.52 |
2 |
Penelopides panini Penelopides manillae |
3 |
6 |
6 |
0 |
15 |
4.53 |
3 |
Penelopides panini Penelopides affinis |
3 |
7 |
5 |
0 |
15 |
3.4 |
4 |
Penelopides samarensis Penelopides affinis |
2 |
5 |
5 |
0 |
12 |
2.06 |
5 |
Buceros hydrocorax hydrocorax Buceros hydrocorax mindanensis |
2 |
7 |
3 |
0 |
12 |
8.85 |
6 |
Buceros hydrocorax hydrocorax Buceros hydrocorax semigaleatus |
2 |
7 |
8 |
0 |
17 |
11.56 |
7 |
Buceros hydrocorax semigaleatus Buceros hydrocorax mindanensis |
2 |
2 |
8 |
0 |
12 |
8.22 |
8 |
Rhabdotorrhinus leucocephalus Rhabdotorrhinus waldeni |
3 |
6 |
6 |
0 |
15 |
5.36 |
The species-pairs of R. leucocephalus vs. R. plicatus and R. waldeni vs. R. plicatus both obtained a score of 7 due to having large effect sizes for bandwidth (7.59 and 9.17), duration (5.99 and 5.60), minimum frequency (15.38 and 18.78), maximum frequency (11.15 and 11.84) and peak frequency (15.15 and 16.43), respectively. Major and exceptional scores were given to the greatest spectral and temporal characters (Table
The species pair of B. h. semigaleatus and B. h. mindanensis had the highest Cohen’s d for bandwidth, minimum frequency, maximum frequency and peak frequency while B. h. hydrocorax vs. B. h. semigaleatus obtained the highest in duration (Table
A small effect size was obtained for the minimum frequency between B. h. hydrocorax vs. B. h. mindanensis (0.29), while large effect sizes for bandwidth (4.86), duration (1.97), maximum frequency (4.94) and peak frequency (4.95) (for the same species pair?). A score of 3 was given to the species pair upon acquiring minor and medium values. In comparison, B. h. hydrocorax vs. B. h. semigaleatus and B. h. semigaleatus vs. B. h. mindanensis, obtained large effect sizes for all vocal characters, hence earning cumulative scores of 8: bandwidth (4.21 and 12.41), duration (11.23 and 19.71), minimum frequency (13.02 and 16.67), maximum frequency (8.58 and 18.34) and peak frequency (13.10 and 16.64), respectively.
In comparison with the Penelopides, Rhabdotorrhinus and Rhyticeros, the allopatric species of Buceros hydrocorax obtained relatively low frequencies. Lower frequencies in Buceros hydrocorax was correlated with the prominent casque size (
As seen in Table
Amongst the endemic Philippine Tarictic hornbills, small effect sizes for the minimum frequency were evident between P. panini and P. samarensis. However, large effect sizes were obtained from the bandwidth, duration, minimum frequency and maximum frequency of P. affinis vs. P. panini, P. affinis vs. P. manillae, P. affinis vs. P. samarensis, P. manillae vs. P. samarensis, P. panini vs. P. samarensis and P. manillae vs. P. panini. A distinctive trumpeting bleat which is highly onomatopoeic of its local name "Tarik-tik" or "Talik-tik", can be collectively referred to all members of the Philippine endemic genus Penelopides. These high pitched calls of Tarictic hornbills are comparable to the similarly toned staccato bark of the genus Rhabdotorrhinus to which they are closely related, but conversely Penelopides have relatively higher frequencies (
QTY |
SPECIES |
RECORDIST |
LOCALITY |
2 |
Penelopides affinis |
Frank Lambert |
Zamboanga, Pasonaca Watershed Reserve, Cabonegro |
1 |
Penelopides affinis |
Frank Lambert |
Mt. Kitanglad, Mindanao |
1 |
Penelopides affinis |
Paul Noakes |
PICOP, Bislig, Mindanao |
1 |
Penelopides affinis |
George Wagner |
Baluno Station, Zamboanga Watershed, Mindanao |
1 |
Penelopides affinis |
David Edwards |
PICOP, Bislig, Mindanao |
4 |
Penelopides manillae |
Shari Guerra |
Avilon Zoo, Rodriguez, Rizal |
1 |
Penelopides manillae |
David Edwards |
Hamut, baliuag, Sierra Madre Mountains, Luzon |
3 |
Penelopides panini |
Shari Guerra |
Avilon Zoo, Rodriguez, Rizal |
1 |
Penelopides panini |
Frank Lambert |
Bacolod, Negros Occidental |
3 |
Penelopides samarensis |
Bram Demeulemeester |
Rajah Sikatuna National Park, Bohol |
1 |
Penelopides samarensis |
Ross Gallardy |
Rajah Sikatuna National Park, Bohol |
3 |
Buceros hydrocorax hydrocorax |
Shari Guerra |
Avilon Zoo, Rodriguez, Rizal |
2 |
Buceros hydrocorax semigaleatus |
Shari Guerra |
Avilon Zoo, Rodriguez, Rizal |
7 |
Buceros hydrocorax mindanensis |
Shari Guerra |
Avilon Zoo, Rodriguez, Rizal |
3 |
Rhabdotorrhinus leucocephalus |
Shari Guerra |
Avilon Zoo, Rodriguez, Rizal |
2 |
Rhabdotorrhinus leucocephalus |
Desmond Allen |
Sitio Siete, South Cotabato Province, Mindanao |
1 |
Rhabdotorrhinus waldeni |
Ross Gallardy |
PICOP, Bislig, Mindanao |
1 |
Rhyticeros plicatus |
Shari Guerra |
Avilon Zoo, Rodriguez, Rizal |
1 |
Rhyticeros plicatus |
Frank Lambert |
Chupukama Ridge, Guadalcanal |
1 |
Rhyticeros plicatus |
Patrick Abueg |
Lolobata National Park, Halmahera, Indonesia |
The above acoustic analyses of the trumpeting calls of Philippine Tarictic hornbills, belonging to the endemic genus Penelopides, support their genus allocation and distinction from the closely related genus Rhabdotorrhinus characterised with its staccato calls (see also Gonzales 2012,
The large effect sizes in the acoustic data, observed amongst subspecies of B. hydrocorax, provide additional support on their proposed taxonomic revisions and potential split, subsequently based on the initial analysis using phenotypic and genetic data presented by