Does the camera create it's own Wi-Fi Network that your phone connects to or can it connect to an existing Wifi network.
eg one of my regular image cameras supports Wi-Fi either it can create a Wi-Fi network eg a network called "Sony-RX100-Wifi-q23ed24" or it can connect to an existing Wi-Fi network (eg from a BT Homehub or whatever Wi-fi you use in the house).
Extending the Wi-fi if it creates its own Wi-fi network is complex (unsure quite how you'd do it, maybe depends on the capabiulities of the wildlife camera which are likely to be "limited").
Extending the house network is more straight forward eg mesh as mentioned above but other options.
It the camera was connecting to the house Wi-fi then standing by a window would make no difference. Were the camera connecting to the house Wi-fi then standing anywhere in the house with good coverage would enable a connection.I've no first hand experience of them, but if you have a spare electric socket by your broadband router and by the window where you can pick up the camera WiFi signal, could you not install a router WiFi extender that sends the through the electric wires?
which suggests they have to be close to the camera to establish a Wi-fi connection directly between phone and camera not phone<->house wi-fi<->Camera Wi-fi.Its connected to my phone via WiFi.
To get a connection i have to stand next to a rear window.
It the camera was connecting to the house Wi-fi then standing by a window would make no difference. Were the camera connecting to the house Wi-fi then standing anywhere in the house with good coverage would enable a connection.
OP asked
which suggests they have to be close to the camera to establish a Wi-fi connection directly between phone and camera not phone<->house wi-fi<->Camera Wi-fi.