Top Gear return nets fewer viewers than last year's series opener
Top Gear, which has been revamped with Matt Le Blanc at the helm alongside co-hosts Chris Harris and Rory Reid, was watched by an average of 2.8 million people, according to overnight data, while Call The Midwife was seen by an average of 8.9 million.
These initial figures do not account for those watching on catch-up at a later time.
Top Gear's series launch in 2016 - with Chris Evans and Le Blanc as new presenters following the departure of long-running hosts Jeremy Clarkson, Richard Hammond and James May - had scored 4.4 million viewers overnight.
Fans praised the new-look show on social media, with former Friends actor Le Blanc as Top Gear's leading man.
Sunday's instalment, which featured a trip to Kazakhstan and an interview with Scottish actor James McAvoy, prompted viewers to describe the new series as a "massive improvement" and that it had made "a promising start".
"Top Gear is back how it should be!" enthused one viewer on Twitter, while another joked the show "was so sweet I could have licked it".
LeBlanc, 49, was called "a natural" as a presenter and several people said the programme was better without Evans, who quit after the last series, saying he gave it his best shot but that it was "not enough".
Last year's series opener was largely savaged by viewers, mainly due to Evans's hosting style.
The decline in audience numbers follows a pattern in recent years, as the motoring magazine show scored higher viewers on average for its series openers with Clarkson, Hammond and May in the driving seat.
The first episode of Top Gear's 2015 series was seen by 5.3 million, and the overall average for the trio's final five years fronting the programme - between 2011 and 2015 - saw an average of 5.2 million viewers per debut episode for every new series.
Meanwhile, Call The Midwife, which concludes its sixth series next Sunday night, has mostly seen a steady increase over the past seven weeks.
The first episode of the series in late January was seen by 7.72 million fans during its broadcast while the overall series average is now at 8.55 million, due to a spike in viewers during its fifth episode at 9.09 million.
Elsewhere, the BBC's alternative reality period drama SS-GB has continued to drop in the ratings as its third episode, which aired on Sunday night at 9pm, scored an overnight average of 3.4 million viewers.
The second episode last week had declined to 3.9 million from the first episode's 6.1 million.
The drama series, an adaptation of Len Deighton's 1978 book of the same name that takes a look at what would have happened if the Nazis had won the Battle of Britain, lost viewers after many complained they found it difficult to hear much of the dialogue.