these bird observations all share the exact same coordinates:
https://www.inaturalist.org/observations/110425352
https://www.inaturalist.org/observations/110425354
https://www.inaturalist.org/observations/110425355
https://www.inaturalist.org/observations/110425356
in such cases, the Explore page map is going to show only one pin, and if you click on the pin, the details for only the latest observation (110425356) are going to be displayed in the pop-up.
there’s an existing feature request to provide some way to indicate that a single map marker represents multiple observations: https://forum.inaturalist.org/t/indicate-overlapping-observations-for-map-pins/18406.