Instead of having an external panel mount puck-style antenna the new birdhouse uses a flexible embedded antenna inside the electronics enclosure (please see the image below). Both antennae are dipoles not requiring a ground plane. The new antenna has the disadvantage of having a solar panel above it which probably affects its radiation pattern.

To compare the performance of the two antennae I gathered some RSSI values using TTN Mapper. In the chart below you can see the average RSSI values for the old (Nr1) and new (Nr2) birdhouse and the LoRaWAN gateways they use. Lower bars (higher RSSI values) in this chart are better. Except for a couple of outliers the new antenna outperformed my expectations. With most gateways the loss is only around 1-2 dB and there are a couple of gateways where the average performance is actually better.