(1-2)   ①  Here is the first harmonic. There are nodes (zero amplitude) at either end, where the string is fixed, and in the exact centre where Cormorant’s wing was touching the string.

②  The higher harmonics must all have nodes at the fixed end points but they differ by having additional nodes in between:

Because the wavelength decreases as the additional nodes are formed, each successive harmonic will sound a higher note.

③   There must be node at either end of the string because it is fixed at those positions. Nodes are formed every half a wavelength, so a standing wave can only be formed if the length of the string is a whole number multiple of the half-wavelength. In other words, if the string has length L, then Cormorant can place his wingtip at a distance of L/2 or L/3 etc from one end, and generate a standing wave. However if he places it 37% of the way along, the only way that can happen is if both the 37% on one side and the 63% on the other side both accommodate exactly a whole number of half-wavelengths. Since these numbers have no common factors other than 1, this can only be achieved by a harmonic having at least 100 half-wavelength elements. Such an extreme distortion of the string would have a negligible amplitude, so would generate, at best, a very faint sound.