The WiFi bird box camera doesn’t work with 5Ghz WiFi. The 5Ghz WiFi provides large bandwidth but a shorter distance. The 2.4Ghz WiFi provides bandwidth more than the IP camera needs, but the penetration capacity (distance) is the IP camera needs more. The wall or trees could weaken the WiFi signal sharply. That is why more than 95% of WiFi IP camera still uses 2.4Ghz.
Most of the dual band routers can provide both 2.4Ghz and 5Ghz WiFi in different names. Some will combine to the single name. You should give the different name to separate 2.4Ghz from 5Ghz.
Firstly, you will need to Log into your router and change the setting. To do this you can use the details on the back of the router to log in or search online for your model of router and how to log into it.
Once logged in you are looking for a setting on how to change the ‘wireless band’ or to ‘enable split banding’ on your router. This is usually in the advanced settings tab but can differ depending on your router. It is a good idea to look online for ‘how to enable 2.4 ghz on [your router model]’.
The below is the reference guide for linksys router.
If you are using mesh WiFi, you can’t separate 2.4Ghz by using a different name. The mesh WiFi requires a single name in the whole system, so you can travel through the different access points. One of the possible solutions is you can add a WiFi repeater or PLC adapter to improve the WiFi signal around the nest box. The PLC adapter usually works in pairs. The transmitter will attach your primary router by using an Ethernet cable. The network will go through the powerline and reach the receiver. The receiver can create a 2.4Ghz WiFi hotspot outside your garden for a WiFi bird box camera connecting. The PLC adapter employs the power line to send the network signal to the garden without punching a hole in the wall.