Study On Calls Of The Crested Ibis(Nipponia Nippon)

Bird songs and calls as one of the most important features, which contain abundant biological information, are vital for the research of Avi-behavior, bird population structure and classification. Among the papers about bird songs and calls, few are about birds of the order Iconiiformes, while most about songbirds. The crested ibis(Nipponia nippon), belonging to the order Iconiiformes, the First-grade state protected animal in China and rare bird in the world, is also animal endemic species of China. Although vanished for a period of time the crested ibis has increased in number with protection since it was rediscovered in Yang county, Shaanxi province, China in 1981. However, the Crested ibis still threatens to extinct because of the small population reproduced by two or three ibis couples. In this paper, for the first time a quantitative analysis of calls of the crested ibis under six status is given, the calls including alert call, mating call, mimic mating call, preen call, flight call and contact call. Then the characteristics of every kind of call are extracted and its biological meanings are discussed, which are useful for the protection of the crested ibis and provide database for the systemic research of the crested ibis' calls and new data for the Chinese bird songs and calls research.Firstly, an all-around summarization of the status of bird songs research and the crested ibis research is presented and the method of acquiring and analyzing the crested ibis calls is introduced. A method of making sonogram on Pc which can display the signal's time-frequency characteristic with the union of time axis, frequency axis and different shades of colors relating to the signals' energy is introduced. Wavelet analysis method is applied to denoise call signals, detect pitch and improve sonogram. The optimum parameters of wavelet denoise are obtained. The result shows that wavelet analysis method can get better effects than traditional methods. In order to conveniently analyze the crested ibis call signals a user interface is established by programming with Matlab language, which can process call signals with wavelet denoise and characteristic analysis—including time-domain analysis, frequency-domain analysis and time-frequency analysis.Secondly, six kinds of the crested ibis call signals are recorded and processed, i.e.alert call, mating call, mimic mating call, preen call, flight call and contact call and the characteristics of every kind of signal are obtained. The result shows that the alert call is monosyllable with duration time 414ms, principal frequency(PF) 1890Hz, Main frequency range(MFR) 300-3450Hz, fundamental frequency(fb) 350Hz. Its sonogram turns out to be multi-harmonic spectrum with ten frequency bands(FB) and half-arched structure. Mating vocal behavior has two stages. The call in the first satge is syllable with duration time 289ms, PF 240Hz, MFR 200-1200Hz, FB number 5, fo 240Hz and in its multi-harmonic spectrum the frequency bands descend with time. The call in the second stage is syllable with duration time 1690ms, PF 860Hz, MFR 300-1300Hz, FB number 7 and in its multi-harmonic spectrum the frequency bands ascend till 270ms and then descend with time. The mimic mating call has three types—monosyllable, disyllable and trisyllable. The monosyllabic mimic mating call, duration time 1093ms, PF 1403Hz, MFR 280-2000Hz, f0 345Hz, multi-harmonic spectrum in which high frequency harmonics vanish with time. The disyllabic mimic mating call, duration time 2320ms(Sl:1320ms, S2:790ms), PF 1420Hz, MFR 205-2100Hz, fo 350Hz, multi-harmonic spectrum in which SI has 13 frequency bands ascending with time and S2 has 8 frequency bands descending with time. The trisyllabic mimic mating call, duration time 1910ms(Sl:907ms, S2:544ms, S3:453ms), PF 1280Hz, MFR 220-2900 Hz, fo325Hz, multi-harmonic spectrum in which SI has 10 frequency bands, S2 has 12 frequency bands and S3 has 5 frequency bands. The preen call, syllable, has two types. The first call type, duration time 760ms, PF 250Hz, MFR 100-2800Hz; the second call type, duration time 480ms, PF 1130Hz, MFR 250-2200Hz, FB number 11, fo 295Hz, multi-harmonic spectrum with line structure. The flight call is syllable with duration time 220ms, PF 1190Hz, MFR 400-1800Hz and its spectrum of equal frequency interval is arched structure. The contact call is syllable with duration time 360ms, PF 807Hz, MFR 200-llOOHz, fb260Hz and its multi-harmonic spectrum is line structure. Among the six kinds of calls the duration time of the disyllabic mimic mating call is longest(2.32s) while that of the flight call shortest(0.22s); PF of the alert call is highest(1890Hz) while that of the mating call in the first stage lowest(240Hz); FB number of the monosyllabic mimic mating is largest(15) while that of the flight call smallest(4). The characteristics of every kind of call are according with the corresponding behavior and can be obviously distinguished.Thirdly, the call differences among the female, male ibis and their associated birds...