Names of Reporting Persons.

I.R.S. Identification Nos. of above persons (entities only).

David L. Payne

Check the Appropriate Box if a Member of a Group (See Instructions)

(a)  ¨        (b)  ¨

SEC Use Only

Citizenship or Place of Organization

United States

Number of

Shares

Beneficially

Owned by

Each

Reporting

Person

With

Sole Voting Power

652,485

Shared Voting Power

345,808

Sole Dispositive Power

652,485

Shared Dispositive Power

345,808

Aggregate Amount Beneficially Owned by Each Reporting Person

998,293

Check if the Aggregate Amount in Row (9) Excludes Certain Shares (See Instructions)  ¨

Percent of Class Represented by Amount in Row (9)

3.58%

Type of Reporting Person (See Instructions)

IN

Names of Reporting Persons.

I.R.S. Identification Nos. of above persons (entities only).

Gibson Radio and Publishing Company

Check the Appropriate Box if a Member of a Group (See Instructions)

(a)  ¨        (b)  ¨

SEC Use Only

Citizenship or Place of Organization

California

Number of

Shares

Beneficially

Owned by

Each

Reporting

Person

With

Sole Voting Power

528,837

Shared Voting Power

0

Sole Dispositive Power

528,837

Shared Dispositive Power

0

Aggregate Amount Beneficially Owned by Each Reporting Person

528,837

Check if the Aggregate Amount in Row (9) Excludes Certain Shares (See Instructions)  ¨

Percent of Class Represented by Amount in Row (9)

1.94%

Type of Reporting Person (See Instructions)

CO

Name of Issuer

Westamerica Bancorporation (“Westamerica”)

Address of Issuer’s Principal Executive Offices

1108 Fifth Avenue

San Rafael, California 94901

Name of Person Filing

This Amendment to Schedule 13G is being filed on behalf of the following persons (“Reporting Persons”)

David L. Payne

Gibson Radio and Publishing Company (the “Company”)

Address of Principal Business Office or, if none, Residence

The principal business office of Mr. Payne is 4550 Mangels Blvd., Fairfield, CA 94534. The principal business office of the Company is 544 Curtola Parkway, Vallejo, CA 94590

Citizenship

David L. Payne: United States

Company, a California Corporation

Title of Class of Securities

This Amendment to Schedule 13G is being filed with respect to the common stock, no par value, of Westamerica (“Common Stock”). The Reporting Persons’ percentage of ownership of Common Stock is based on 27,213,453 shares of Common Stock Outstanding and the ownership of options to purchase 641,099 of Common Stock (the “Options”) held by Mr. Payne.

As of December 31, 2012 (i) Mr. Payne beneficially owned 998,293 shares of Common Stock, of which 641,099 shares are attributable to the Options; and (ii) the Company beneficially owned 528,837 shares of Common Stock, none of which are attributable to the Options.

CUSIP Number

957090103

If this statement is filed pursuant to §§240.13d-1(b) or 240.13d-2(b) or (c), check whether the person filing is a:

Not applicable as this Amendment to Schedule 13G is filed pursuant to Rule 13d-1(c).

¨       Broker or dealer registered under section 15 of the Act (15 U.S.C. 78o).

¨       Bank as defined in section 3(a)(6) of the Act (15 U.S.C. 78c).

¨       Insurance company as defined in section 3(a)(19) of the Act (15 U.S.C. 78c).

¨       Investment company registered under section 8 of the Investment Company Act of 1940 (15 U.S.C 80a-8).

¨       An investment adviser in accordance with §240.13d-1(b)(1)(ii)(E);

¨       An employee benefit plan or endowment fund in accordance with §240.13d-1(b)(1)(ii)(F);

¨       A parent holding company or control person in accordance with § 240.13d-1(b)(1)(ii)(G);

¨       A savings associations as defined in Section 3(b) of the Federal Deposit Insurance Act (12 U.S.C. 1813);

¨       A church plan that is excluded from the definition of an investment company under section 3(c)(14) of the Investment Company Act of 1940 (15 U.S.C. 80a-3);

¨       Group, in accordance with §240.13d-1(b)(1)(ii)(J).

Ownership.

The information in items 1 and 5 through 11 on pages 2-3 of this Amendment to Schedule 13G is hereby incorporated by reference.

The 998,293 shares of Common Stock reported in row 9 on page 2 of this Amendment to Schedule 13G: (i) include 345,808 shares held in a revocable trust, as to which Mr. Payne is a co-trustee, and (ii) exclude the 528,837 shares owned by the Company, of which Mr. Payne is President and CEO. Mr. Payne expressly disclaims beneficial ownership of these shares.

If this statement is being filed to report the fact that as of the date hereof the reporting person has ceased to be the beneficial owner of more than five percent of the class of securities, check the following  ¨.

Instruction: Dissolution of a group requires a response to this item.

Ownership of More than Five Percent on Behalf of Another Person.

The Company does not have any voting or dispositive power over the shares of Common Stock beneficially owned by Mr. Payne, and it expressly disclaims beneficial ownership of his shares.

Identification and Classification of the Subsidiary Which Acquired the Security Being Reported on By the Parent Holding Company or Control Person.

Not applicable.

Identification and Classification of Members of the Group

Not applicable.

Notice of Dissolution of Group

Not applicable

Certification:

The following certification shall be included if the statement is filed pursuant to §240.13d-1(c):