The pink/purple birds/ducks indicate different types of marine sanctuaries or estuary area zones/nature reserve areas. These can be environmentally sensitive sea areas or areas with minor restrictions and/or information notices. The same icon is used in the NOAA (government) charts: https://nauticalcharts.noaa.gov/publications/us-chart-1.html
, on page 72.
These icons are present on the "Restricted" layer of charting detail, which can be turned off on some units. Please note: turning off the Restricted layer, aka Caution Areas, will also turn off the boundaries, etc. that are useful for navigation.
The example below shows the difference with the Caution Areas turned on and off on a Raymarine unit:
For Raymarine units that allow this option to be turned off, go to Presentation>Objects>Caution Areas>switch ON/OFF.
For Navico units that allow this option to be turned off, go to Chart Details>User>Restricted Area>switch ON/OFF.
For Humminbird units that allow this option to be turned off, go to the Chart Tab>Chart Detail Levels>Custom Chart Layers>Restricted Areas>switch ON/OFF.