Hi Hanna and Welcome to the forum:
As always, the decision to upgrade is a challenging one. So, to try to guide your thinking I have a few observations and questions for you to ponder.
My Understanding: You say that you have a 35mm and 50mm lens, and want to do wildlife photography, particularly birds and you have a budget of about $1,000.
Here is your dilemma: if you want an APS-C camera that is part of the R-series with IBIS and animal eye tracking, then you are correct in saying that the R7 is the most likely body. You could go for a lesser body like the R10, R50 or R100, but as wildlife cameras they will miss out on IBIS, which is not critical, but very helpful.
However, that body alone will not come within your budget and that is not even considering the lens you need for bird photography. I have been shooting wildlife for four decades and can say that for birds you need something in the region of 400-600mm, even with a crop-sensor camera and such an optic alone is likely to push you well towards $1k and well past that with a Mirrorless Interchangeable Lens Camera (MILC).
You need to examine your budget, especially in light of your statement that you "want dive into it", (I was initially confused by your typo).
Thinking Laterally: If your budget is limited, and you don't want to or can't invest more, but want the reach, then the alternative is to consider what you will produce in the context of the sensor size. If you are prepared to go to a smaller sensor, then you could consider the focal lengths you can achieve by getting a Bridge Super Zoom camera, such as the PowerShot SX70HS. This has a smaller sensor, but give you an equivalent focal range of 21-1365mm, which will really bring subjects closer to you.
The consideration of output comes in here: the kind of output has a significant impact on what you actually need to produce for the medium to which you are intending to publish. Essentially, it requires a lot more investment to achieve detailed, Fine Art prints for sale compared with publishing to social media or digital display. Thus, if you don't need to do more than post on the web or show on a digital device, you could get the reach without the significant investment.
To give you an idea of the range of the lens with this camera: These were taken with the SX60HS, which has the same sensor and lens as the current PowerShot SX70HS. The files I am showing have been seriously downsized to fit into the 5MB limit for posting to this site, and the 900mm is oddly noisy due to that. I encourage you to click on the series and see them full screen. Furthermore, at super long FLs, one is also going to get heat haze, as in this case.
This is a screen shot of a slide from a course I run on buying camera gear, it shows the relative qualities of two images by two cameras massively different in price. The prices quoted were in Canadian dollars and are some years past, but the principle is still valid.
While the two cameras considered are not the R7 and SX70, the 7DII has similar image quality and the SX60 is actually functionally identical to the SX70HS as far as sensor and lens go.
Furthermore, since you say you are interested in pursuing post production, whatever shortcomings come with the smaller sensor may be offset by the significant improvements that AI has brought to improving resolution and reducing noise in post-production software like Photoshop, Lightroom, or with deVinci Noise AI, Topaz Sharpen AI, or Topaz Photo AI.
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