Why are there no special effects of seagulls in the clip?

Because the software version and material library do not support it. At present, editing software provides a rich library of video special effects and materials, including words, stickers, filters, transitions, music and so on. Users can choose and edit according to their own needs. If you need to use the "Seagull" special effect, you can try to search for related materials or special effects in the material library or other resource libraries, or edit and make them with other software.