In this reading it is the swan, immortalized in 鸿鹄之志 ('the ambition of the great swan') — a metaphor for soaring aspirations beyond the grasp of small minds. The compound 鹄立 means to stand waiting with a long, swan-like neck.
mistakes
Don't read 鸿鹄 as 'hónghào'. As the swan and in this fixed phrase the reading is hú; the gǔ reading belongs only to the separate 'target / bull's-eye' sense.
The bird radical 鸟 on the right marks the literal meaning in the swan reading — a large water bird. The separate gǔ 'target' sense borrows the same written form.
Supplies the sound. Standalone 告 reads gào; the reading drifted to hú (and gǔ for the target sense). It is the phonetic element, carrying no meaning to the bird.
